| ClockingSystems | |
| Clockstudio | |
| ClockTowerWeb | Berkshire |
| Clockwork Bear | Swansea |
| Clockwork Creative Technology Ltd | |
| Clockwork Marketing | Devon |
| CLOK | |
| Cloobees UK Ltd | Greater London |
| Close Brothers Group plc | |
| Closed Loop Medicine | |
| Closir | |
| Cloud & Cyber Security Expo | Greater London |
| Cloud 9 Digital Design Ltd | |
| Cloud AI Tech | |
| Cloud and More | |
| Cloud Appreciation | |
| Cloud Capture Ltd | |
| Cloud Computing News | Bristol |
| Cloud Cover | |
| Cloud Cover Hosting Ltd | Cornwall |
| Cloud Create | |
| Cloud Cycle Ltd | |
| Cloud Dot Ini | |
| Cloud Employee | |
| Cloud Energy | |
| Cloud Essentials | Somerset |
| Cloud Fulfilment | |
| Cloud Global | |
| Cloud Industry Forum | |
| Cloud Maker | |
| Cloud Orca Ltd | |
| Cloud Precision | |
| Cloud Smart Solutions Ltd | Buckinghamshire |
| Cloud Technology Solutions Ltd | Greater Manchester |
| Cloud Wireless | |
| Cloud8 | East Sussex |
| Cloud8 Ltd | |
| Cloud9 Systems | Greater London |
| Cloudabove | |
| CloudApps Ltd | Berkshire |
| Cloudblue Web Design | Nottinghamshire |
| CloudBound | |
| CloudBuy | |
| CloudCoCo Group plc | |
| CloudConnX Ltd | |
| CloudDirect | Berkshire |
| Cloudest | |
| Cloudev Ltd | Greater London |
| CloudFactory Ltd | |
| Cloudfind Ltd | |