| PO Number | Town / Place name | Code |
|---|---|---|
| 400 | Ilfracombe | |
| 401 | Ilminster | |
| 402 | Ingatestone | |
| 403 | Rayleigh | |
| Erith | ||
| 404 | Wickford | |
| Belvedere | ||
| 405 | Ipswich | |
| 406 | Ironbridge | |
| 407 | Douglas, IOM | |
| 408 | Ivy Bridge | |
| 409 | Jersey | |
| 410 | Kelvedon | |
| 411 | Kendall | |
| 412 | Bowness | |
| Picardy Belvedere | ||
| 413 | Keswick | |
| 414 | Kettering | |
| 415 | Kidderminster | |
| 416 | Kimbolton | |
| 417 | Kineton | |
| Hucknall Torkard | ||
| 418 | Kingsbridge | |
| 419 | Kington | |
| 420 | Pennybont | |
| 421 | Radnor | |
| Long Eaton | ||
| 422 | Kingston | |
| Kingston on Thames | ||
| 423 | Kirkby Lonsdale | |
| New Charlton | ||
| 424 | Knaresborough | |
| 425 | Knutsford | |
| 426 | Lamberhurst | |
| Crowhill Ross | ||
| 427 | Hawkhurst | |
| 428 | Hurst Green | |
| 429 | Newenden | |
| Broxbourne | ||
| 430 | Northiam | |
| Headcorn | ||
| 431 | Peamarsh | |
| 432 | Rolvenden | |
| Croesgoch | ||
| 433 | Sandhurst | |
| Maesteg | ||
| 434 | Lampeter | |
| 435 | Aberaeron | |
| 436 | Lancaster | |
| 437 | Kirkby Stephen | |
| 438 | Sedburgh | |
| 439 | Launceston | |
| 440 | Holsworthy | |
| 441 | Stratton | |
| 442 | Bude | |
| 443 | Lowton | |
| Aberkenfig | ||
| 444 | Leamington | |
| 445 | Leatherhead | |
| 446 | Ledbury | |
| 447 | Leeds (C) | |
| Chapeltown Rd. B.O. Leeds | ||
| Hunslet B.O. Leeds | ||
| Hyde Park B.O. Leeds | ||
| Hyde Park Corner B.O. Leeds | ||
| 448 | Leek | |
| 449 | Leicester | |
| 450 | Leighton Buzzard | |
| 451 | Lewes | |
| Lewes Station Office | ||
| 452 | Newhaven | |
| Porthcawl | ||
| 453 | Seaford | |
| Llanfairfechan | ||
| 454 | Leominster | |
| 455 | Pembridge | |
| 456 | Shobden | |
| Shobdon | ||
| 457 | Lichfield | |
| 458 | Lincoln | |
| Lincoln Sorting Tender | ||
| 459 | Kirton-in-Lindsey | |
| Kirton-Lindsay | ||
| 460 | Wragby | |
| 461 | Linton | |
| Upper Bangor | ||
| 462 | Liphook | |
| 463 | Liskeard | |
| 464 | Looe | |
| Hessle | ||
| 465 | Polperro | |
| Llangenech | ||
| 466 | Liverpool | |
| Liverpool Exchange (C) | ||
| Bootle Liverpool | ||
| Bootle-cum-Linacre Liverpool | ||
| Liverpool E. | ||
| Liverpool N. | ||
| Liverpool S. | ||
| Liverpool E.D. | ||
| Liverpool S.D. | ||
| Liverpool W.D. | ||
| Liverpool N.D. | ||
| 467 | Llandeilo | |
| 468 | Llandovery | |
| 469 | Llanely | |
| 470 | Pontardulais | |
| Ponterdulais | ||
| 471 | Llangadock | |
| 472 | Llangollen | |
| 473 | Long Stratton | |
| 474 | Lostwithiel | |
| 475 | Loughborough | |
| 476 | Mountsorrel | |
| 477 | Louth | |
| 478 | Lowestoft | |
| 479 | Ludlow | |
| 480 | Knighton | |
| 481 | Leintwardine | |
| Haslemere | ||
| 482 | Luton | |
| 483 | Lutterworth | |
| 484 | Lyme | |
| Lyme Regis | ||
| 485 | Lymington | |
| 486 | Yarmouth, IOW | |
| 487 | Lyndhurst | |
| 488 | Lynn | |
| King's Lynn | ||
| 489 | Burnham | |
| Hildenborough | ||
| 490 | Holkham | |
| Ham Street | ||
| 491 | Macclesfield | |
| 492 | Maidenhead | |
| 493 | Maidstone | |
| Maidstone Station Office | ||
| 494 | Maldon | |
| 495 | Malton | |
| 496 | Sledmere | |
| Kew | ||
| 497 | Malvern | |
| 498 | Manchester | |
| Manchester E. | ||
| Manchester N. (C) | ||
| Manchester N.W. | ||
| Manchester S. | ||
| Manchester S. DO. | ||
| Manchester S.E. | ||
| Manchester S.W. | ||
| Manchester W. | ||
| 499 | Glossop |