| Code | Name | Region |
|---|---|---|
| GBJOG | John O'groats | HLD |
| GBJHV | Johnshaven | ABD |
| GBJHT | Johnstone | RFW |
| GBJTB | Johnstonebridge | DGY |
| GBJGR | Juniper Green | EDH |
| GBJUR | Jura | AGB |
| GBIRT | Irchester | NTH |
| GBIRL | Irlam | TRF |
| GBIAO | Iron Acton | SGC |
| GBIBG | Ironbridge | SHR |
| GBIVL | Ironville | DBY |
| GBIIB | Irthlingborough | NTH |
| GBIRV | Irvine | NAY |
| GBIVT | Irvinestown | FER |
| GBIOD | Isfield | ESX |
| GBIMG | Islandmagee | ANT |
| GBISY | Islay | AGB |
| GBILY | Islay Apt | AGB |
| GBIAB | Isle Abbotts | SOM |
| GBIAR | Isle Of Barra | ELS |
| GBIOG | Isle Of Grain | KEN |
| GBIOP | Isle Of Portland | DOR |
| GBIOS | Isle Of Sheppey | KEN |
| GBISK | Isle Of Skye | HLD |
| GBSKY | Isle Of Skye Apt | |
| GBWHH | Isle Of Whithorn | DGY |
| GBIGM | Ingoldmells | LIN |
| GBICD | Inkberrow | WOR |
| GBITH | Innerleithen | SCB |
| GBISH | Insch | ABD |
| GBINS | Instow | DEV |
| GBIAY | Inverallochy | ABD |
| GBIVR | Inveraray | AGB |
| GBIVB | Inverbervie | ABD |
| GBINY | Invergarry | HLD |
| GBIVG | Invergordon | HLD |
| GBINR | Inverie | HLD |
| GBINK | Inverkeithing | FIF |
| GBIVK | Inverkip | IVC |
| GBIVV | Invermoriston | SCB |
| GBINV | Inverness | HLD |
| GBIND | Invernoaden | AGB |
| GBIRG | Inveruglas | AGB |
| GBIVI | Inverurie | ABD |
| GBIPS | Ipswich | SFK |
| GBIRB | Irby | CON |
| GBIDC | Idlicote | OXF |
| GBICT | Ilchester | SOM |
| GBIFD | Ilford | NWM |
| GBILF | Ilfracombe |