| Code | Name | Region |
|---|---|---|
| GBMWO | Mansfield Woodhouse | NTT |
| GBMSE | Manston | KEN |
| GBE9X | Manuden | ESS |
| GBMRZ | Marazion | CON |
| GBMAR | March | CAM |
| GBMRC | Marchington | STS |
| GBMWI | Marchwiel | WRX |
| GBMAW | Marchwood | HAM |
| GBMRD | Marden | KEN |
| GBMRF | Marfleet | KHL |
| GBMGM | Margam | NTL |
| GBMGT | Margate | KEN |
| GBMBT | Market Bosworth | LEC |
| GBMDP | Market Deeping | CAM |
| GBMKD | Market Drayton | SHR |
| GBMKH | Market Harborough | LEC |
| GBMAH | Maidenhead | WNM |
| GBMAI | Maidens | |
| GBMDT | Maidstone | KEN |
| GBMSD | Maitresse Island | |
| GBMBH | Malborough | DEV |
| GBMAL | Maldon | ESS |
| GBMLG | Mallaig | HLD |
| GBMLK | Mallusk/newtownabbey | NTA |
| GBMMB | Malmesbury | WIL |
| GBMCH | Malpas | CHW |
| GBMLY | Maltby | ROT |
| GBMLN | Malton | NYK |
| GBZCA | Malvern Link | WOR |
| GBMVW | Malvern Wells | WOR |
| GBMHI | Mamhilad | MON |
| GBMNY | Manby | LIN |
| GBMCR | Mancetter | WAR |
| GBMNC | Manchester | MAN |
| GBMAN | Manchester Container Terminal | |
| GBMSC | Manchester Ship Canal, Salford | MAN |
| GBMCM | Macmerry | ELN |
| GBMAD | Maddiston | FAL |
| GBMDY | Madeley | STS |
| GBMAE | Madeley | TFW |
| GBMDX | Madley | HEF |
| GBMEY | Maerdy | CWY |
| GBMEE | Maesteg | BGE |
| GBMYW | Maesycwmmer | CAY |
| GBMGR | Magdalen Laver | ESS |
| GBMHA | Maghera | MFT |
| GBMGH | Maghera | NBL |
| GBMFT | Magherafelt | MFT |
| GBMGN | Magheramason | DRY |
| GBMGO | Magheramorne |