| Compounding LAB Ltd | Hornchurch | 2023 |
| Compre Commodities Ltd | London | 2025 |
| Comprehensive Access Services Ltd | London | 2020 |
| Comprehensive Elevator Services Limited | London | 2006 |
| Compressed Air & Refrigeration Services Limited | Wednesbury | 2010 |
| Compressed Air Centre Industrial Utility Management Ltd | Chessington | 2025 |
| Compressed Air Centre Limited | Chessington | 1992 |
| Compressed Air Contracts (Scotland) Limited | East Kilbride | 2008 |
| Compressed Air Energy Solutions Ltd | Redditch | 2024 |
| Compressed Air Engineering (Redditch) Ltd | Redditch | 2010 |
| Compressed Air Group Ltd | Chessington | 2025 |
| Compressed Air Services (Worcester) Limited | Bromyard | 2003 |
| Compressed Air Solutions Limited | Cosby | 2005 |
| Compressed Air Technologies Ltd | Milton Keynes | 2008 |
| Compressed GAS Solutions Limited | Deeside | 2008 |
| Compression Ignition Power Solutions Ltd. | Leek | 2017 |
| Compressive Materials Limited | Haverhill | 2025 |
| Compressor Installation Services Limited | Winners Wokingham | 1993 |
| Compressor Maintenance Services Limited | St. Helens | 1998 |
| Compressor Maintenance Systems Limited | Maidstone | 2012 |
| Compressor Products International Limited | Hungerford | 1984 |
| Compressor Sales Service and Repairs Ltd | Bridgnorth | 2025 |
| Compressor Services International Limited | North Shields | 1986 |
| Compressor Services Ltd | Co. Down | 1996 |
| Compressor Solutions Ltd | Swansea | 2012 |
| Compressor Systems (West) Limited | Bristol | 2000 |
| Compressors & Air Equipment Ltd | Leicester | 1988 |
| Compressors & Pneumatic Systems Limited | Aylesbury | 2007 |
| Compressors and General Engineering Ltd | Holmfirth | 2019 |
| Compressors and Pipework Systems Limited | Roxwell | 2019 |
| Compressors Limited | Alfreton | 1984 |
| Compressortech Limited | Warwick | 1994 |
| COMPROMISE2015 Ltd | Wolverhampton | 2015 |
| Compson Electrical Services Limited | Uxbridge | 2011 |
| Comptec Limited | Walsall | 1996 |
| Comptech Solutions Ltd | Basingstoke | 2024 |
| Compton Carpentry Ltd | Shanklin | 2023 |
| Compton Fabrications Ltd | Ferndale | 2022 |
| Compton GSR Limited | Bristol | 2011 |
| Compton Printing Limited | Burgess Hill | 1992 |
| Compton Products Limited | Newquay | 1996 |
| Compton-Associates Ltd | Solihull | 2007 |
| Comptons 2000 Limited | West Midlands | 2000 |
| Compton’S Kitchens Ltd | Faversham | 2020 |
| Compucharge Limited | Wickford | 2003 |
| Compugaming Ltd | London | 2025 |
| Compugrafix Ltd | London | 2015 |
| Compugraphics International Limited | Woking | 1967 |
| Compurent Limited | Nelson | 1995 |
| Compusystems UK Limited | Crawley | 1995 |
| Computacables Limited | Walsall | 2010 |
| Compute and Cultivate Ltd | Leeds | 2023 |
| Computech Turning Limited | Ashton-Under-Lyne | 2000 |
| Computer & Laptop Repair Services Limited | Chester Le Street | 2013 |
| Computer Audio Design Limited | Horsham | 2010 |
| Computer Business Forms Limited | Wirral | 1983 |
| Computer Controlled Cutting Limited | Ramsgate | 2021 |
| Computer Controlled Solutions Limited | Kenilworth | 1996 |
| Computer Imprintable Label Systems Limited | Hove | 1987 |
| Computer Monitoring and Control Limited | Manchester | 1988 |
| Computer Recyclers (UK) Ltd | Penygraig | 2010 |
| Computer Room Services Ltd | Stevenage | 2023 |
| Computer Systems UK Ltd. | Bishops Stortford | 1988 |
| Computerised Cutting Technology Services Limited | Stockport | 1999 |
| Computerko Limited | London | 2017 |
| Computers 4 Business Ltd | Orpington | 2010 |
| Computers by Design Direct Limited | Stowmarket | 2010 |
| Computers Online Limited | Berkshire | 2000 |
| Computing Europe Limited | Mid Glamorgan | 2001 |
| Computionics Limited | Hilldale,Parbold | 1981 |
| Computype Europe Limited | London | 1983 |
| Compz Ltd | Woodbridge | 2025 |
| Comranado UK Ltd | London | 2023 |
| Comres Limited | Bradford | 2019 |
| Comrie Estates Ltd | London | 2016 |
| Comsafe Tech Services Limited | Kingswinford | 2013 |
| Comsove Global Operations Limited | London | 2024 |
| Comtech Engineers Ltd. | Cardiff | 2011 |
| Comtech Research Limited | Brentford | 2016 |
| Comtek Ltd | Thetford | 2001 |
| Comtherm Limited | Droitwich | 1989 |
| Comtrad Tech Ltd | Sheffield | 2021 |
| Comtrex Systems Corporation Limited | Abingdon | 1978 |
| Comunidade Europeia DE Trafego Ltd | Wembley | 2021 |
| Comus Europe Limited | Brightlingsea | 1989 |
| Comve Engineers Ltd | London | 2013 |
| Comvel Steel Productions Ltd | London | 2025 |
| Comvic Ltd | Cambridge | 2025 |
| Comyn Ching & Co. (Solray) Limited | Gorseinon | 1976 |
| CON GAS Games Ltd | Lydbury North | 2015 |
| CON Mech Durham 2 Limited | Manchester | 1988 |
| CON Mech Engineers Limited | Stanley | 1960 |
| CON Mech Group Limited | Darlington | 1949 |
| CON Tech (Ireland) Limited | Cookstown | 2023 |
| Con-Sole Group Ltd | Kings Langley | 2026 |
| Con-Tech Services Limited | Barnsley | 1986 |
| Con-Tempo Furniture Limited | Salisbury | 2018 |
| Conal Kielty Enterprises Limited | Belfast | 2016 |
| Conan Sturdy, Blacksmith Ltd | London | 2019 |
| Conares UK Limited | Leicester | 2021 |