| PO Number | Town / Place name | Code |
|---|---|---|
| 700 | Sheffield | |
| 701 | Shepton Mallet | |
| 702 | Sherbourne | |
| 703 | Queen Camel | |
| Hatherleigh | ||
| 704 | South Shields | |
| 705 | Shifnall | |
| Shiffnall | ||
| 706 | Shipston | |
| Shipston on Stour | ||
| 707 | Shorehame | |
| 708 | Shrewsbury | |
| 709 | Church Stretton | |
| 710 | Llandiloes | |
| 711 | Wem | |
| 712 | Sidmouth | |
| 713 | Sittingbourne | |
| 714 | Skipton | |
| 715 | Cross Hills | |
| 716 | Sleaford | |
| 717 | Slough | |
| 718 | Colnbrook | |
| Manorbier | ||
| 719 | Solihull | |
| Fourstones | ||
| 720 | Somerton | |
| 721 | Langport | |
| 722 | Southam | |
| 723 | Southampton | |
| 724 | South Molton | |
| 725 | South Petherton | |
| 726 | Martock | |
| 727 | Spalding | |
| 728 | Spilsby | |
| 729 | Spittal | |
| 730 | Stafford | |
| Stafford Station | ||
| 731 | Stilton | |
| Spelter Works | ||
| Caerau Bridgend | ||
| 732 | Stockbridge | |
| South Stockton | ||
| Thornaby on Tees | ||
| 733 | Stockport | |
| 734 | Disley | |
| Whalley | ||
| 735 | Hazelgrove | |
| Trecastle | ||
| 736 | Stockton | |
| Stockton on Tees | ||
| 737 | Castle Eden | |
| Broadstairs | ||
| Broadstairs Station Office B.O. | ||
| 738 | Stokenchurch | |
| Byfield | ||
| 739 | Stokesley | |
| 740 | Ingleby | |
| Crawley Down | ||
| 741 | Staines | |
| 742 | Stamford | |
| 743 | Stevenage | |
| 744 | Steyning | |
| 745 | Stone, Staffs | |
| 746 | Stoneham | |
| 747 | Thwaite | |
| Nantyfyllon | ||
| 748 | Stoney Cross | |
| Newson Heath | ||
| 749 | Stoney Stratford | |
| Stony Stratford | ||
| 750 | Stourbridge | |
| 751 | Stourport | |
| 752 | Stowmarket | |
| 753 | Needham Market | |
| 754 | Stratford on Avon | |
| 755 | Alcester | |
| 756 | Henley in Arden | |
| Budleigh Salterton | ||
| 757 | Stroud | |
| 758 | Kingscote | |
| 759 | Uley | |
| 760 | Sudbury | |
| 761 | Sunderland | |
| 762 | Swaffham | |
| 763 | Swansea | |
| The Docks Swansea | ||
| The Docks B.O. Swansea | ||
| Swansea Mumbles | ||
| St. Helens Swansea | ||
| Swansea Walters Rd. | ||
| 764 | Brinmawr | |
| Brynmawr, Brec. | ||
| 765 | Reynoldstone | |
| Partridge Green | ||
| 766 | Swindon | |
| New Swindon | ||
| 767 | Cricklade | |
| 768 | Wootton Bassett | |
| 769 | Wroughton | |
| 770 | Stanmore | |
| 771 | Shooters Hill | |
| Caerphilly | ||
| 772 | Tadcaster | |
| 773 | Taibach Aberavon | |
| Port Talbot | ||
| 774 | Tamworth | |
| 775 | Tarporley | |
| 776 | Taunton | |
| 777 | Williton | |
| 778 | Dunster | |
| 779 | Minehead | |
| 780 | Tavistock | |
| 781 | Callington | |
| 782 | Teignmouth | |
| 783 | Tenbury | |
| 784 | Tenby | |
| 785 | Tenterden | |
| 786 | Tetbury | |
| 787 | Tetsworth | |
| 788 | Tewkesbury | |
| 789 | Thame | |
| 790 | Thetford | |
| 791 | Harling | |
| E. Harling | ||
| 792 | Larlingford | |
| New Tredegar | ||
| 793 | Shipdam | |
| Sandringham | ||
| 794 | Watton | |
| Watton, Norfolk | ||
| 795 | Thirsk | |
| 796 | Osmotherley | |
| West Wickham | ||
| 797 | Thorne | |
| Kibworth Harcourt | ||
| 798 | Thrapstone | |
| Thrapston | ||
| 799 | Tipton |