| Matrix Science Ltd | |
| Matrix Web Design | |
| Matt Gray | |
| Matt Jackson | |
| Matt Kersley | Cambridgeshire |
| Matt's Computer Solutions | West Sussex |
| Matter of Fact Software Ltd | |
| Matter of Focus | |
| Matthew Hart | |
| Matthews Computer Services | Berkshire |
| Matttech Modular | |
| Mauriweb Network Ltd | Oxfordshire |
| MauveCom Ltd | Hampshire |
| Maven Capital Partners UK, LLP | |
| Maven IT Services Ltd | Kent |
| Maverick Automation | |
| Mawbray Web Design | North Yorkshire |
| MAX IT Services Ltd | Herefordshire |
| Max Web Solutions | |
| Max Websites | |
| Max Your Web Ltd | |
| Maxell Europe Ltd | Berkshire |
| Maxima Systems Ltd | Isle of Man |
| Maximon Solutions | Buckinghamshire |
| Maximum Network Solutions | South Yorkshire |
| Maxion Therapeutics | |
| MaxLogic, LLP | |
| Maxnett Ltd | |
| MAXX Design Ltd | Berkshire |
| Maya Capital, LLP | |
| Maya Tech Media | |
| Mayfair Digital Marketing | |
| Mayfair Ventures | |
| Mayfin Design Ltd | Fife |
| Mayfly Internet Marketing Ltd | Merseyside |
| Mayman Design Ltd | West Midlands |
| Mays Website Designers | |
| Maytech | |
| Maze | |
| Maze House Medical | |
| Maze Theory | |
| Maznet | Hertfordshire |
| MB Web Design | |
| Mbed | |
| MBL Solutions | Northumberland |
| MBS Survey Software Ltd | |
| MCA Communications | Mid-Ulster |
| MCC Systems Ltd | Cornwall |
| McCann Connected | Greater Manchester |
| McCann Erickson Central Ltd | |