| ComputerDocOnline.co.uk | Berkshire |
| Computerhelp @ Home | |
| Computerisation Ltd | Cardiff |
| ComputerMinds Ltd | Bristol |
| Computers 4 Charity | Kent |
| Computers In Personnel Ltd | Buckinghamshire |
| Computerstar | |
| ComputerSurgery.com | Edinburgh |
| ComputerTel Ltd | |
| ComputerWare | Berkshire |
| ComputerWeekly.com | |
| ComputerWorld Group | |
| Computime Ltd | |
| Computing | |
| Computing At School | Wiltshire |
| Computing Cubed Ltd | |
| Computing Dynamics Ltd | Northamptonshire |
| Computing Help Ltd | Greater Manchester |
| Computors Ltd | West Midlands |
| CompuWeb Communications Services Ltd | Nottinghamshire |
| Compuwight Computer Services | Isle of Wight |
| Comsci | |
| Comsci Ltd | Hampshire |
| Comtec Cable Accessories Ltd | Cambridgeshire |
| Comtec-Group Ltd | Cardiff |
| Comtech Support (Scotland) Ltd | |
| Comtek System Solutions | County Durham |
| Comtrex Systems | Surrey |
| CoMutiny | |
| Conatus Financing Solutions Ltd | |
| Concentric | Greater London |
| Concentric Health Ltd | |
| Concentric Marketing Ltd | East Sussex |
| Concept Cables Ltd | Dorset |
| Concept CAD Ltd | Nottinghamshire |
| Concept First | Devon |
| Concept I.T. Consultancy | Merseyside |
| Concept Integrated Systems | |
| Concept Life Sciences | Derbyshire |
| Concept NI Web Solutions | Mid-Ulster |
| Concept Northern | South Lanarkshire |
| Concept Soft | |
| Concept Solutions People | West Yorkshire |
| Concept VC Ltd | Greater London |
| Concept Ventures | |
| Concept Web Design Glasgow | Glasgow |
| Conceptdigital | |
| Concert Networks | Cheshire |
| ConchX | |
| Concinnity Genetics | |