| Code | Name | Region |
|---|---|---|
| GBASG | Ardrishaig | AGB |
| GBARD | Ardrossan | NAY |
| GBADE | Ardsley East = Ardsley | LDS |
| GBARV | Ardveenish | ELS |
| GBMDI | Ardwick | MAN |
| GBDYN | Ardyne | AGB |
| GBVLY | Anglesey | AGY |
| GBANB | Anlaby | |
| GBANG | Annalong | NYM |
| GBANN | Annan | DGY |
| GBANE | Annesley | NTT |
| GBANW | Annesley Woodhouse | NTT |
| GBANP | Annfield Plain | DUR |
| GBANS | Anstruther | FIF |
| GBAW3 | Ansty | WAR |
| GBATY | Ansty | WSX |
| GBANT | Antrim | ANT |
| GBAYB | Apperley Bridge | |
| GBAPI | Appin | AGB |
| GBAZV | Appleby | CMA |
| GBAP2 | Appleby | NLN |
| GBAPS | Applecross | HLD |
| GBAPP | Appledore | |
| GBAPL | Appleton | OXF |
| GBAPT | Appleton Thorn | CHW |
| GBABR | Appley Bridge | LAN |
| GBACM | Altrincham | TRF |
| GBALA | Alva | CLK |
| GBAVH | Alvechurch | WOR |
| GBAVL | Alveley | SHR |
| GBALV | Alveston | SGC |
| GBALT | Alyth | PKN |
| GBAMG | Ambergate | DBY |
| GBAMB | Amble | NBL |
| GBAML | Ambleside | CMA |
| GBAME | Amersham | BKM |
| GBAMS | Amesbury | WIL |
| GBAMW | Amlwch | AGY |
| GBAMM | Ammanford | CMN |
| GBAM9 | Ampfield | HAM |
| GBAMP | Ampthill | CBF |
| GBANA | Anasuria | SCT |
| GBAN2 | Ancaster | LIN |
| GBAN9 | Anderton | CHW |
| GBAVR | Andover | HAM |
| GBADV | Andoversford | GLS |
| GBAFT | Alfriston | ESX |
| GBASE | Allestree | DBY |
| GBKK6 | Allington | KEN |
| GBGTG | Allington | LIN |