| Chichele Property Company (ASC) Limited | Oxford | 1996 |
| Chicksgrove Quarry Limited | Cheltenham | 1997 |
| Chile Chemical Mining (Europe) Co., Ltd | Cambridge | 2025 |
| Chile Chemical Mining (Netherlands) Limited | West Midlands, England | 2025 |
| China Agricultural Group International Agricultural Supplies (UK) Development Co., Ltd | Cambridge | 2025 |
| China Agricultural Supply and Marketing Group Trading Co., Limited | London | 2024 |
| China Ocean Group Ltd | London | 2019 |
| Chok LOM Fluids Services Limited | Altrincham | 2009 |
| Chord Town Leatherworks Ltd | London | 2025 |
| Chorley Sand & Aggregates Limited | Chorley | 1999 |
| Chris Blair Crushing Services Limited | | 2007 |
| Chris Dykes International Ltd. | Aberdeen | 2002 |
| Chris FEE Ltd | Gateshead | 2026 |
| Chrismik Ltd | Montrose | 2017 |
| Christie Geosolutions Ltd | Fen Drayton | 2018 |
| Christopher Milburn Limited | Choppington | 2016 |
| Chromex Mining Limited | London | 2005 |
| Chrysaor (U.K.) Alpha Limited | London | 1989 |
| Chrysaor (U.K.) Beta Limited | London | 1988 |
| Chrysaor (U.K.) Britannia Limited | London | 1994 |
| Chrysaor (U.K.) Sigma Limited | London | 2011 |
| Chrysaor (U.K.) Theta Limited | London | 1980 |
| Chrysaor CNS Limited | London | 2009 |
| Chrysaor Developments Limited | London | 1987 |
| Chrysaor E&P Limited | London | 2017 |
| Chrysaor Limited | London | 2007 |
| Chrysaor North Sea Limited | London | 1969 |
| Chrysaor Petroleum Company U.K. Limited | London | 1964 |
| Chrysaor Petroleum Limited | London | 1976 |
| Chrysaor Production (U.K.) Limited | London | 1953 |
| Chrysaor Production Holdings Limited | London | 1998 |
| Chrysaor Resources (Irish Sea) Limited | London | 1997 |
| Churchill Stone (N.I.) Limited | Derry | 2011 |
| Chute Technologies Ltd | London | 2026 |
| Chwarel Bryncir Quarry Prosesu Dwyfach Processing CYF | Ruthin | 2008 |
| Cieco West Qurna Limited | London | 2017 |
| Cies International Limited | Tonbridge | 2019 |
| Cimpanu Ltd | Leicester | 2025 |
| Cinero Group Ltd | Birmingham | 2026 |
| Cipora Ltd | Ilford | 2026 |
| Circular Resources (Technologies) Limited | London | 2023 |
| Cirque Energy (UK) Limited | Taunton | 1995 |
| Citipaving Company Limited | Rayleigh | 2008 |
| City's Vape Ltd | Coventry | 2024 |
| CJ & JB Services Ltd | Lowestoft | 2026 |
| CJ Sky Ltd | Aberdeen | 2021 |
| CJ Well Services Ltd | Norwich | 2023 |
| CJD Contracts NI Limited | Cookstown | 2020 |
| CJD Subsea Ltd | Fraserburgh | 2024 |
| CJH Aggregate Ltd | Market Harborough | 2019 |
| CJS Drilling Services Limited | Stonehaven | 2007 |
| CK Corporation Ltd | London | 2021 |
| CK Electrical Access Limited | Stockton-On-Tees | 2016 |
| CKA Rigging and Lifting Services Limited | Middlesbrough | 2018 |
| CL Drilling Services Limited | Aberdeen | 2023 |
| CL Offshore Ltd | Limavady | 2022 |
| CL Offshore Project Management Limited | Aberdeen | 2008 |
| Clach Mara Ltd | Glasgow | 2025 |
| Clach Supplies Ltd | Kilmarnock | 2025 |
| Clachan Geoscience Ltd | Aberdeen | 2019 |
| Cladachatom Limited | London | 2022 |
| Clady Aggregates Limited | Armagh | 2022 |
| Clady Quarries Plant & Hire Ltd | Armagh | 2012 |
| Claims Validation Services Limited | Tavistock | 1996 |
| Clan Well Services Ltd | Broughty Ferry | 2025 |
| Clara Petroleum Ltd | London | 2008 |
| Claremont Subsea Services Limited | Laurencekirk | 2011 |
| Clarence Energy Services Limited | London | 2020 |
| Clarity Marble & Tiles Ltd | Morden | 2023 |
| Clark's Offshore Ltd | Lowestoft | 2016 |
| Clarke Quarries Ltd | Londonderry | 2016 |
| Classictask Limited | Liverpool | 2010 |
| Claw Engineering Ltd | Lowestoft | 2024 |
| Claxton Engineering Services Limited | Great Yarmouth | 1985 |
| Clay Consultants Limited | Knaresborough | 2005 |
| Claydon Exploration Ltd | Chipping Campden | 2018 |
| Cleanlandfill Co. Limited | Lichfield | 1998 |
| Cleansorb Limited | London | 1994 |
| Cleantech Lithium Ltd | London | 2020 |
| Clearserve Limited | Stanford-Le-Hope | 1995 |
| Cles Fonctionnel Limited | Cardiff | 2021 |
| Clevedon Materials Processing Consultancy Limited | Buxton | 2017 |
| Cleveland Potash Limited | Saltburn By The Sea | 1967 |
| Clgj Ltd | Blackpool | 2019 |
| Clieve Holdings Limited | St. Austell | 2016 |
| Clipsham Quarry Company Limited | Helpson | 1964 |
| Clipsham Stone Cutting Company Limited | Nottingham | 2017 |
| Clive Hurt Anglesey Limited | Ruthin | 2009 |
| Cllb Process HSE Ltd | Grimsby | 2026 |
| Cloburn Quarry Company Limited | Lanark | 1985 |
| Clockrocks Holdings Ltd | Birmingham | 2023 |
| Cloell Solutions Limited | Swansea | 2015 |
| Clogher Valley Materials Limited | Omagh | 2024 |
| Clontarf Energy PLC | London | 2003 |
| Cloudcast Limited | Basildon | 1984 |
| Clover Drilling Services Limited | Totland | 1995 |
| Cloverview Management Solutions Ltd | Turriff | 2009 |
| CLS Global Solutions Limited | Dartford | 2014 |
| Clubb Sand and Gravel Ltd | Fareham | 1947 |
| Clubb's Washed Gravel Company Limited | Fareham | 1956 |