Disclosure: This guide is published by Cloom Tech. Cloom Tech is one of the ten companies listed below, and the decision block at the end is a sponsored, disclosed element that routes you to Cloom Tech.
Custom cable assemblies and wire harnesses span a wide range of specialisms — from hermetic vacuum feedthroughs to rail-assurance-scheme-registered harness builders — so the right UK supplier for one buyer can be the wrong one for another. This guide does not rank suppliers. It sets out what to check and gives the same facts for each company so you can compare them yourself.
What should I check before shortlisting a UK custom cable assembly company?
Use these criteria for every company in this guide:
- Quality system: which certifications the company publishes, and whether it names the specific site or scope the certificate covers.
- Where it’s actually built: the company’s own stated manufacturing location(s). A UK-registered or UK-branded company can still build overseas, or have UK, European and Far East sites under one group.
- Scale and facility fit: facility size, headcount or output figures the company publishes, and whether they suit your production volume.
- Specialist capability: whether the company publishes a specific capability relevant to your build — overmoulding, hermetic/vacuum sealing, RF/microwave assemblies, rail-assurance-scheme registration, or branded-connector distribution — rather than generic cable assembly only.
- What’s actually published vs. what’s claimed elsewhere: figures below come from each company’s own website unless marked otherwise. Anything a company did not publish is stated as not published, not estimated.
Which UK custom cable assembly companies are there to choose from?
The ten companies are listed in alphabetical order. Order does not indicate quality or preference.
Cloom Tech (Hebei Cloom Electronic Technology Co., Ltd)
Cloom Tech is one of the ten companies in this guide. Its facts below use the company’s own published figures.
- Founded: 2017.
- Locations: Shijiazhuang, Hebei, China (headquarters and plant, 5,000 m² facility); Cavite, Philippines (plant, near Manila); Medley, Florida, USA (office).
- Certifications (company-stated): ISO 9001; IATF 16949 (valid to August 2029 — this specific expiry date is not shown on the live site checked in this pass); ISO 13485 (shown as a certification badge on the company’s own site, without accompanying certificate detail); IPC/WHMA-A-620E CIS (operator and inspector qualification — not shown on the live site checked in this pass).
- Focus: custom OEM wire harnesses and cable assemblies built to customer specifications; states 1,000+ cumulative clients since 2017. It does not supply standalone connectors or off-the-shelf/pre-built harnesses, and offers recommendations rather than a full design service.
Trade-offs:
- Strength: an IATF 16949 certificate and a stated 5,000 m² facility, plus an ISO 13485 badge suggesting medical-grade harness capability.
- Limit: builds in China and the Philippines with a US office only — no UK or European site — so confirm production location, lead time and import/customs handling into the UK before ordering.
Cornelius Electronics (Cornelius Electronics Ltd)
- Founded: the company’s own site gives two different dates in two different places — a company-history page says “Cornelius Electronics was founded in 1979,” while a separate on-page section says “Established In 1983.” The site does not reconcile these.
- Locations: Port Talbot, South Wales, UK (single site, about 50,000 sq ft). Workforce is also stated inconsistently — “220+ Operatives” in one section, “250+ Fully Trained Employees” in another.
- Certifications (company-stated): ISO 9001; ISO 14001; UL/CSA.
- Focus: contract-manufactured wiring harnesses, cable assemblies, box builds, overmoulding and vacuum forming. Its own site names “transportation equipment, medical products, data centres, telecoms and industrial machinery” as its core service list, and separately lists EV & automotive, renewables, rail and telematics among sectors served.
Trade-offs:
- Strength: one large UK site (about 50,000 sq ft) covering harness assembly, box build, overmoulding and vacuum forming together.
- Limit: the company’s own site gives conflicting founding dates and headcount figures in different places, so confirm current figures directly; ask which specific site/scope its certificates cover.
Greenstock
- Founded: not published on the company’s own site as of this check.
- Locations: Lincoln, UK (Unit H, Hillcroft Business Park, Whisby Road). Facility size, employee count and export-country count are not published on the pages checked.
- Certifications (company-stated): a Cyber Essentials badge, and an “IPC” logo without a named standard. ISO 9001 is not named on the pages checked.
- Focus: overmoulding (cable, connector and low-pressure), PCB encapsulation, injection moulding, and custom cable/wire-harness design and assembly, plus box builds for OEM customers.
Trade-offs:
- Strength: overmoulding and PCB-encapsulation capability alongside standard cable assembly, in one UK site.
- Limit: founding year, headcount, export reach and a named ISO quality certificate are not published on the pages checked, so ask for current figures and certificates directly.
GTK UK (GTK UK Ltd)
- Founded: 1990.
- Locations: the company’s own site describes manufacturing in “the UK, Romania and the Far East” without naming cities or facility sizes. Its listed phone number carries a Basingstoke, Hampshire (01256) dialling code.
- Certifications (company-stated): the site links to a “Quality Certificates” downloads page and an “Our Certifications” section under each market page, but the certificate names themselves were not retrievable as page text in this pass.
- Focus: custom cable assemblies, wiring harnesses, overmoulded and waterproof assemblies, RF cable assemblies and display cable assemblies, each described as “bespoke to individual customer specifications.” Its own site names transport & automotive, industrial, medical, test & measurement, security, broadcast & communications, and consumer & retail among the markets it serves.
Trade-offs:
- Strength: multi-site manufacturing (UK, Romania, Far East) under one group, with a wide published range of custom assembly types and named markets.
- Limit: specific certifications, facility sizes and sector case-study detail were not retrievable from the company’s own site as of this check, so ask for the certificate and site that would cover your build directly.
Jacarem Ltd
- Founded: not published on the company’s own site as of this check (“decades of expertise” and “supplying connectors across the globe for decades” are the only claims).
- Locations: Chesham, Buckinghamshire, UK (single site).
- Certifications (company-stated): the site shows an unlabelled “isoc compliance” logo in the footer; no named ISO or IPC standard appears on the pages checked.
- Focus: franchise distributor for connector brands including Positronic, ODU, ERNI, Conec, Souriau, EDAC, Sonitron, Emulation Technology and MH Connectors; UK manufacture of cable assemblies and hermetic/vacuum-sealed products (vacuum feedthroughs, flanges, viewports) for medical devices and industrial equipment; general connectors and cable assemblies for telecommunications, automotive, consumer electronics, industrial automation, medical technology and renewable energy.
Trade-offs:
- Strength: a specialised hermetic-sealing and vacuum-feedthrough product line alongside standard connector distribution, spanning several other named sectors.
- Limit: founding year and specific quality certifications are not published on the pages checked, so ask for them directly before relying on it for certified work.
Leotronics
- Founded: 1990.
- Locations: Rake, Hampshire, UK (head office and warehouse). The company’s own site also states it holds stock in the UK and Far East, is part of the Conexcon Group, and has warehousing across Europe plus a Hong Kong facility.
- Certifications (company-stated): ISO 9001:2015; UL; CSA. ISO 14001 and RoHS are not named on the pages checked, despite a general claim elsewhere on the site of being “fully certified by the ISO.”
- Focus: custom cable assemblies, cable harness assemblies, IDC and FFC cables, and board-to-board/wire-to-board/wire-to-wire connectors, positioned as alternatives to Molex, Samtec and JST parts; design, manufacturing, sourcing and worldwide distribution.
Trade-offs:
- Strength: a named, dated ISO 9001:2015 certificate and group-level warehousing (UK, Europe, Hong Kong, Far East stock).
- Limit: the site does not name a specific industry sector it serves beyond “various electronics and technology based industries worldwide,” so ask for sector-specific references before assuming fit for your application.
MSH Electronics
- Founded: not published on the company’s own site as of this check (“over 25 years” is the only claim).
- Locations: Wimborne, Dorset, UK (single site, 2,000 sq ft).
- Certifications (company-stated): ISO 9001. IPC/WHMA-A-620 is not named on the pages checked.
- Focus: cable assembly, wire harnesses, contract electronic manufacturing and wire preparation, with prototyping support. The company’s own site names Communications, Automotive, Security, Oil and Business among the sectors it serves.
Trade-offs:
- Strength: a focused operation that names specific served sectors directly on its own site.
- Limit: a 2,000 sq ft facility is small relative to several others in this guide, so confirm capacity and lead times for your volume; a founding year is not published.
RCL Global (RCL Connectors & Cables Ltd)
- Founded: 2005.
- Locations: Redruth, Cornwall, UK (Unit 4 Wood Mine Business Park). Its listed phone number carries a Swindon (01793) dialling code, though no Swindon site address is published on the pages checked.
- Certifications (company-stated): not published on the pages checked.
- Focus: network cabling and bespoke cable-assembly supply, including fibre and data-networking products, with import and mass-production support. Its own site’s project case studies describe airport data-communications upgrades (Manchester, Gatwick, Edinburgh, plus CCTV cabling for a major London airport), a telecoms 4G rollout, rail infrastructure supply, and a time-critical cruise-ship AV cable delivery.
Trade-offs:
- Strength: documented, varied project case studies (airports, a telecoms rollout, rail, marine/leisure) published on its own site.
- Limit: no certification is published on the pages checked, so ask for the specific standard and certificate that would apply to your order.
Scott Cables (Scott Cables Ltd)
- Founded: established 1990 as Select Enterprises; renamed Select Cables, then Scott Cables in 2012.
- Locations: Portsmouth, Hampshire, UK (Unit 7 Merlin Park).
- Certifications (company-stated): the site has a “Certifications & Approvals” section with clickable icons, but no certificate names are shown as page text on the pages checked.
- Focus: custom cable assemblies for rail (rolling stock, trackside and infrastructure applications; registered with the UK rail supplier-assurance scheme RISQS), automotive (no minimum order quantity; ruggedised or lightweight harnesses; growing electric/hybrid-vehicle demand) and motorsport, plus telecoms and broadcast work as European Master Distributor for Times Microwave Systems since 2001.
Trade-offs:
- Strength: a RISQS rail-supplier registration and a long-standing (2001–) distribution agreement with Times Microwave for telecoms/broadcast RF work.
- Limit: no certificate name is published as page text despite a dedicated certifications section, so ask for the specific standard and document before relying on it for regulated work.
St Cross Electronics
- Founded: 1979.
- Locations: Southampton, Hampshire, UK (single site, Mount Pleasant Industrial Park); the company states all production stays at this one site with nothing subcontracted offshore.
- Certifications (company-stated): ISO 9001:2015 (stated as verified by ISOQAR); ISO 14001; ISO 45001 (the site also cites the superseded OHSAS 18001 standard alongside ISO 45001 without reconciling the two).
- Focus: cable assembly and wire-harness manufacturing from single prototypes up to batches of over 100,000 units, using automated cut/strip/crimp/test machinery and ERP-based scheduling, with 100% electrical testing before dispatch. Its own site names medical and motorsport/F1 wiring harnesses among its work, with Cirris-tested harnesses specifically called out for motorsport.
Trade-offs:
- Strength: a single UK site handling everything in-house, prototype through 100,000+-unit batches, with 100% electrical test on every unit.
- Limit: this guide can only describe its medical and motorsport work; the company’s own site states other named specialisms that are out of scope for this guide, so ask directly whether your specific use case is one it builds most often.
How do I choose between these suppliers?
- Match the certificate to the site, not just the company. Several companies here publish a certifications section without naming the standard or the site it covers — ask for the actual certificate before assuming group-wide coverage.
- Confirm the build location. A UK-registered or UK-branded company may build in the UK, Europe or the Far East (or several). Ask for the plant address in writing.
- Check scale fit. A 2,000 sq ft single-site operation and a multi-country group serve different kinds of orders — match the supplier’s published scale to your volume.
- Ask about the specific capability you need — overmoulding, hermetic/vacuum sealing, RF/microwave, rail-assurance registration, or branded-connector sourcing — rather than assuming general cable-assembly experience covers it.
- Send the same drawing to two or three suppliers and compare lead time, questions asked, and MOQ.
Ready to request a quote?
Sponsored (Cloom Tech): If you want Cloom Tech to quote your assembly, send your drawing, expected volumes and target certifications. Request a quote at the Cloom Tech contact page. See what Cloom Tech builds as a custom cable assembly manufacturer.
