| C&I UK Holdings Limited | Newbury | 2026 |
| C&J Antich Ltd | Huddersfield | 2010 |
| C&J Cakes Ltd | London | 2021 |
| C&J Contracts Ltd | Liverpool | 2025 |
| C&J Welding Ltd | Wednesbury | 2022 |
| C&K Fabrications Ltd | Hinckley | 2026 |
| C&K Gardiner (Holdings) Limited | Swindon | 2025 |
| C&K Mcdonnell Ltd | Dromore | 2020 |
| C&L Carpentry (Southern) Limited | Lee-On-The-Solent | 2015 |
| C&L Lead Sheet Fabrication Limited | Penarth | 2011 |
| C&M Clinical Engineering Solutions Ltd | Cardiff | 2020 |
| C&M Licensing Ltd | Co Tyrone | 2006 |
| C&M Meals Ltd | Bath | 2021 |
| C&M Projects (Oldham) Ltd | Oldham | 2012 |
| C&M Services Ltd | Buckie | 2024 |
| C&M Waste Machinery Ltd | Dungannon | 2025 |
| C&O Joinery Ltd | Birmingham | 2023 |
| C&R Carpentry & Renovations Limited | Oxfordshire | 2021 |
| C&R Electrical and Electronic Services Limited | Hull | 2000 |
| C&R Fibre Optik Ltd | Dagenham | 2025 |
| C&R Logistics Ltd | Borehamwood | 2019 |
| C&R Scotland Limited | Edinburgh | 2026 |
| C&S Aero Limited | Porthcawl | 2015 |
| C&S Butcher & Catering Ltd | Carrickfergus | 2022 |
| C&S Carpentry Ltd | Gloucester | 2023 |
| C&S Controls Limited | Bexleyheath | 2009 |
| C&S Embroidery Ltd | Kidderminster | 2024 |
| C&S Global Ltd | Southend-On-Sea | 2022 |
| C&S Heating Ltd | Armagh | 2025 |
| C&S Precision ENG Ltd | Omagh | 2014 |
| C&Sjewels Ltd | London | 2019 |
| C&Sons London Ltd | London | 2019 |
| C&T Doors and Windows Limited | Wolverhampton | 2004 |
| C&T Weaving Ltd | Glasgow | 2020 |
| C&T Welding Ltd | Barrow-In-Furness | 2025 |
| C&V Building Maintenance Limited | Ilford | 2019 |
| C&V Import Ltd | Harrogate | 2020 |
| C&W Interiors Limited | Rayleigh | 2022 |
| C&Z Kitchen Limited | Welwyn Garden City | 2024 |
| C, Maxtone Ltd | Elgin | 2021 |
| C-130 Total Maintenance Ltd | Cambridge | 2025 |
| C-Air Filtration Limited | Accrington | 2014 |
| C-B-C Metal Fabrication Limited | Glasgow | 2021 |
| C-Caps (UK) Ltd | | 1998 |
| C-Cell Limited | Warrington | 2003 |
| C-Concept Studio Ltd. | London | 2018 |
| C-Dec Holdings Ltd | Livingston | 2025 |
| C-Dent Ltd | London | 2020 |
| C-Fix Limited | King'S Lynn | 2015 |
| C-Fret Festival Limited | Driffield | 2022 |
| C-Fury Limited | Shrewsbury | 2001 |
| C-Kab Mouldings Limited | Heywood | 2010 |
| C-Lect Medical Limited | Doncaster | 2000 |
| C-Loop Packaging UK Limited | Reading | 2022 |
| C-Mac Motorsport Limited | Erskine | 2026 |
| C-Mac SMT Limited | Warwick | 2018 |
| C-Made Ltd | London | 2018 |
| C-Major Limited | High Wycombe | 2005 |
| C-Matik Ltd | Bolton | 2025 |
| C-Max Limited | Dorchester | 1992 |
| C-Mos Engineering Solutions Limited | Chester Le Street | 2025 |
| C-Net Industrial Solutions Limited | Smethwick | 2004 |
| C-Padel Limited | Warrington | 2026 |
| C-Paste Limited | Lancaster | 2020 |
| C-Pro Direct Ltd. | Edenbridge | 1997 |
| C-Probe Structures Limited | St. Helens | 2018 |
| C-Scope International Holdings Limited | Wotton Road, Ashford | 1984 |
| C-Sics Ltd | Watford | 2023 |
| C-Sure Limited | Birkenhead | 2020 |
| C-Tec Germany Limited | Lytham | 2008 |
| C-Tec Limited | Leighton Buzzard | 1996 |
| C-Tech Composites Limited | Chesham | 1998 |
| C-Tech Dental and Medical Digital Imaging Ltd | London | 2022 |
| C-Tech Garage Equipment Services Ltd | Glasgow | 2020 |
| C-Tex Limited | Warwick | 2015 |
| C-Tine Drinks Ltd | London | 2026 |
| C-Trak Limited | Leighton Buzzard | 1981 |
| C-Zero Limited | London | 2024 |
| C. & a. Roberts Limited | London | 1915 |
| C. & B. Steels Limited | | 1965 |
| C. & E. Plant Sales (Chard) Limited | Chard | 1978 |
| C. & G. Tool & Cutter Co. Limited | Swansea | 1975 |
| C. & H. Quick-Mix Limited | Norwich | 1965 |
| C. & J. Clark (Services) Limited | Somerset | 1968 |
| C. & K. Extrusions Limited | Tavistock Square | 1972 |
| C. & P. Control Panel Services Ltd | Swansea | 2023 |
| C. & P. Engineering Services Limited | Swansea | 1973 |
| C. & S. (Neath) Steel Services Limited | Neath | 1979 |
| C. & S. (Port Talbot) Limited | Neath | 1959 |
| C. & S. Cladding (Wales) Limited | Dyfed | 1990 |
| C. & S. Fabrications Limited | Sheffield | 1983 |
| C. & S. Instrument Services Limited | Benfleet | 1973 |
| C. & T. Engineering Limited | Weston Super Mare | 1983 |
| C. & V. Carmichael Limited | Cowdenbeath | 1988 |
| C. a. Designs (Leicester) Limited | Moulton Park | 1996 |
| C. a. Hendley (Essex) Limited | London | 1978 |
| C. a. Mackenzie Limited | Edinburgh | 2019 |
| C. a. Parkinson Electrical Contractors Ltd. | Leeds | 2019 |
| C. and K. Precision Engineers Limited | Stoke-On-Trent | 1984 |
| C. and R. Furniture (Armagh) Limited | Co Armagh | 1973 |