| Code | Name | Region |
|---|---|---|
| GBMFN | Morfa Nefyn | GWN |
| GBMXK | Morley | LDS |
| GBZEF | Morningside | NLK |
| GBMOR | Morpeth | NBL |
| GBMRS | Morston | NFK |
| GBMTM | Mortimer Common | HAM |
| GBMTZ | Mortlake | RIC |
| GBMRO | Morton | LIN |
| GBMSB | Mossbank | ZET |
| GBZCG | Mossend | NLK |
| GBOSY | Mossley | TAM |
| GBMSS | Mossley Hill | LIV |
| GBMMR | Mossmoran | |
| GBMOS | Moston | MAN |
| GBCHE | Mostyn | FLN |
| GBMOW | Motherwell | NLK |
| GBMKO | Monkton | STY |
| GBMMO | Monmouth | MON |
| GBMNE | Montacute | SOM |
| GBMTR | Montgomery | POW |
| GBMMY | Montgomery Trefaldwyn | |
| GBMON | Montrose | ANS |
| GBZCC | Moodiesburn | NLK |
| GBMRW | Moor Row | CMA |
| GBMXO | Moore | HAL |
| GBXMO | Moore Cheshire | HAL |
| GBMOG | Moorgate | LND |
| GBMTW | Moortown | LDS |
| GBZCE | Morden | DOR |
| GBMOD | Morden | STN |
| GBMOC | Morecambe | LAN |
| GBMOY | Moresby | CMA |
| GBMTD | Morestead | HAM |
| GBMRT | Moreton | DOR |
| GBMOT | Moreton | WRL |
| GBMNU | Moreton On Lugg | HEF |
| GBMIN | Minworth | BIR |
| GBMIR | Mirfield | KIR |
| GBM89 | Miserden | GLS |
| GBMST | Misterton | NTT |
| GBMIS | Mistley | ESS |
| GBMTC | Mitcham | MRT |
| GBMIT | Mitcheldean | GLS |
| GBMCE | Mitchem | SRY |
| GBMTI | Mitton | STS |
| GBMNS | Moaness, Hoy | ORK |
| GBMOB | Mobberley | CHE |
| GBMHE | Mochdre | |
| GBMFR | Moelfre | AGY |
| GBMRR | Moelfre Roads |