| Code | Name | Region |
|---|---|---|
| GBMOF | Moffat | DGY |
| GBMQR | Moira | LEC |
| GBMOA | Moira | LSB |
| GBMOL | Mold | FLN |
| GBMLS | Molesworth | CAM |
| GBMNO | Monkton | SAY |
| GBMLM | Millom | CMA |
| GBMLP | Millport, Great Cumbrae | NAY |
| GBMTB | Milltimber | ABD |
| GBMWA | Millwall | |
| GBMLT | Milnathort | PKN |
| GBMLV | Milngavie | EDU |
| GBMLO | Milnrow | RCH |
| GBMNP | Milnthorpe | CMA |
| GBMIL | Milton | KEN |
| GBMAB | Milton Abbas | DOR |
| GBZDQ | Milton Bridge | |
| GBMIK | Milton Keynes | BKM |
| GBMLC | Milton Of Campsie | GLG |
| GBMIO | Milton, Abingdon | OXF |
| GBXMV | Milverton | |
| GBMNA | Minchinhampton | GLS |
| GBMHD | Minehead | SOM |
| GBMVL | Minster Lovell | OXF |
| GBMSW | Minsterworth | GLS |
| GBMNW | Mintlaw | ABD |
| GBRGN | Mid Glamorgan | ESX |
| GBMYE | Mid Yell | ZET |
| GBMDD | Middlefield Law | RCC |
| GBMDL | Middleham | NYK |
| GBMID | Middlesbrough | RCC |
| GBMDZ | Middlesex | LND |
| GBMDN | Middleton | RCH |
| GBMD3 | Middleton | WAR |
| GBMDW | Middlewich | CHE |
| GBMDH | Midhurst | WSX |
| GBMSM | Midsomer Norton | SOM |
| GBMDO | Milden | SFK |
| GBMLL | Mildenhall | SFK |
| GBMPG | Miles Platting | MAN |
| GBXMI | Milfield | NBL |
| GBMKF | Milford | SRY |
| GBMLF | Milford Haven | PEM |
| GBMFS | Milford-on-sea | HAM |
| GBMHL | Mill Hill | BEN |
| GBMLB | Millbrook | CON |
| GBMEI | Merriott | SOM |
| GBMYD | Merseyside | LIV |
| GBME5 | Merstham | SRY |
| GBMET | Merthyr Tydfil | MTY |