| Code | Name | Region |
|---|---|---|
| GBMEO | Merton | MRT |
| GBMER | Merton | NFK |
| GBMSG | Messingham | |
| GBMEF | Metfield | SFK |
| GBXME | Metheringham | LIN |
| GBMTH | Methil | FIF |
| GBMTK | Methlick | ABD |
| GBMTV | Methven | PKN |
| GBMWD | Methwold | NFK |
| GBMVG | Mevagissey | CON |
| GBMXB | Mexborough | ROT |
| GBMDS | Micheldever | HAM |
| GBMKE | Mickfield | SFK |
| GBMKT | Mickle Trafford | CHW |
| GBOMF | Micklefield | LDS |
| GBMCO | Mickleton | GLS |
| GBMLH | Melksham | WIL |
| GBMLJ | Mellor | SKP |
| GBMML | Melmerby | CMA |
| GBMEM | Melmerby | NYK |
| GBMLR | Melrose | SCB |
| GBZCB | Melsonby | NYK |
| GBMLA | Meltham | KIR |
| GBMTO | Melton | SFK |
| GBMNT | Melton Constable | NFK |
| GBMBY | Melton Mowbray | LEC |
| GBMBU | Membury | DEV |
| GBMEB | Menai Bridge | GWN |
| GBMEN | Mendlesham | SFK |
| GBMSR | Menstrie | CLK |
| GBMBR | Meole Brace | SHR |
| GBMPM | Meopham | KEN |
| GBMHJ | Meppershall | CBF |
| GBMRE | Mere | WIL |
| GBMWH | Mereworth | KEN |
| GBMRQ | Meriden | SOL |
| GBMKB | Matlock Bath | DBY |
| GBMTY | Mattersey | NTT |
| GBEEH | Mauchline | EAY |
| GBMUD | Maulden | CBF |
| GBMWG | Mawgan | CON |
| GBMYB | Maybole | SAY |
| GBMYN | Maydown | DRY |
| GBMYF | Mayfair | WSM |
| GBMSX | Mayfield | ESX |
| GBMAY | Mayfield | MLN |
| GBMYS | Maylandsea | ESS |
| GBMSA | Measham | LEC |
| GBMED | Med | MDW |
| GBMMH | Medmenham | BKM |