| PO Number | Town / Place name | Code |
|---|---|---|
| 600 | Addingham | |
| 601 | Oundle | |
| 602 | Ongar | |
| 603 | Oxford | |
| 604 | Pembroke | |
| 605 | Penkridge | |
| 606 | Penrith | |
| 607 | Alston | |
| 608 | Penryn | |
| 609 | Penzance | |
| 610 | Scilly | |
| 611 | Pershore | |
| 612 | Peterborough | |
| 613 | Petersfield | |
| 614 | Petworth | |
| 615 | Fittleworth | |
| 616 | Pulborough | |
| 617 | Storrington | |
| 618 | Pewsey | |
| 619 | Pickering | |
| 620 | Plymouth | |
| 621 | Plympton | |
| 622 | Pocklington | |
| 623 | Pontefract | |
| 624 | Poole | |
| 625 | Portsmouth (C) | |
| Portsmouth H.P.O. | ||
| High St. B.O. Portsmouth | ||
| Landport Portsmouth | ||
| Portsea Portsmouth | ||
| 626 | Prescot | |
| 627 | Presteign | |
| 628 | Preston | |
| 629 | Fleetwood | |
| 630 | Preston Brook | |
| 631 | Frodsham | |
| 632 | Pwllheli | |
| 633 | Queensborough | |
| 634 | Ramsgate | |
| 635 | Reading | |
| 636 | Redruth | |
| 637 | Reigate | |
| 638 | Retford | |
| 639 | Rhayader | |
| 640 | Devil's Bridge | |
| 641 | Richmond, Yorks | |
| 642 | Ravenglass | |
| 643 | Rickmansworth | |
| 644 | Ringwood | |
| 645 | Ripley | |
| 646 | Ripon | |
| 647 | Robertsbridge | |
| 648 | Rochdale | |
| 649 | Littleborough | |
| Snodland | ||
| 650 | Rochester | |
| 651 | Rochford | |
| 652 | Rockingham | |
| Crymmych | ||
| 653 | Romsey | |
| 654 | Ross | |
| 655 | Rotherham | |
| 656 | Wath | |
| Bingham | ||
| 657 | Rougham | |
| 658 | Royston | |
| 659 | Rugby | |
| Rugby Station | ||
| 660 | Rugeley | |
| 661 | Great Heywood | |
| Rotherfield | ||
| 662 | Shirlewich | |
| Sowerby Bridge | ||
| 663 | Wolsey Bridge | |
| Feltham | ||
| 664 | Rushyford | |
| Ilkley | ||
| 665 | Ruthin | |
| 666 | Ryde, IOW | |
| 667 | Rye | |
| 668 | Romford | |
| 669 | Saffron Waldon | |
| 670 | St. Austell | |
| 671 | Grampound | |
| 672 | St. Mawes | |
| West Woodburn | ||
| 673 | Mevagissey | |
| 674 | Tregoney | |
| Great Chestererford | ||
| 675 | St. Albans | |
| 676 | St. Asaph | |
| 677 | St. Clear's | |
| 678 | St. Coloumb | |
| 679 | St. Helen's | |
| 680 | St. Ives, Hunts | |
| 681 | Somersham | |
| Dunkenfield | ||
| 682 | St. Leonard's (C) | |
| St. Leonard's on Sea | ||
| Borough Green, Kent | ||
| 683 | Salisbury | |
| 684 | Downton | |
| 685 | Wilton | |
| 686 | St. Neots | |
| 687 | Sandbach | |
| 688 | Sandwich | |
| 689 | Sawbridgeworth | |
| 690 | Saxmundham | |
| 691 | Aldeborough | |
| Eglwyswrw | ||
| 692 | Yoxford | |
| Velindre | ||
| 693 | Scarborough | |
| 694 | Scole | |
| 695 | Selby | |
| 696 | Settle | |
| 697 | Sevenoaks | |
| 698 | Shaftesbury | |
| Shaftsbury | ||
| 699 | Sheerness |