| Code | Name | Region |
|---|---|---|
| GBSZM | Soham | CAM |
| GBSOL | Solihull | SOL |
| GBSLV | Solva (solfach) | PEM |
| GBSRB | Somerby | LEC |
| GBSOM | Somercotes | DBY |
| GBSMB | Somersby | LIN |
| GBSMR | Somerton | SOM |
| GBSPT | Sompting | WSX |
| GBSQN | Sonning | WOK |
| GBSUU | Soulbury | BKM |
| GBSUT | South Arne | |
| GBOBN | South Bank | |
| GBSBF | South Benfleet | ESS |
| GBOUH | South Brent | DEV |
| GBSTC | South Cave | ERY |
| GBSKN | South Cornelly | BGE |
| GBSKR | Skerray | HLD |
| GBSKW | Skewen | NTL |
| GBIDY | Skidby | ERY |
| GBSGV | Skinningrove | |
| GBSKI | Skipton | NYK |
| GBSKP | Skipton On Swale | NYK |
| GBSLW | Slawston | LEC |
| GBSLE | Sleaford | LIN |
| GBATS | Sleat | HLD |
| GBSLI | Slinfold | WSX |
| GBSY5 | Slingsby | NYK |
| GBSLO | Slough | SLG |
| GBSMD | Small Dole | WSX |
| GBSJJ | Small Heath | BIR |
| GBSMF | Smallfield | SRY |
| GBSMT | Smarden | KEN |
| GBSME | Smethwick | SAW |
| GBSIW | Snailwell | CAM |
| GBVBC | Snaith | ERY |
| GBSID | Snape Bridge | |
| GBSLY | Sileby | LEC |
| GBSIL | Silloth | CMA |
| GBSSD | Silsden | BRD |
| GBISO | Silsoe | CBF |
| GBVST | Silverstone | NTT |
| GBSVE | Silverton | |
| GBSVT | Silvertown | |
| GBSMO | Simonstone | LAN |
| GBSMW | Simonswood | LAN |
| GBSIN | Singleton | LAN |
| GBSNG | Singleton | WSX |
| GBSSG | Sissinghurst | KEN |
| GBSIT | Sittingbourne | KEN |
| GBSZB | Sizewell Beach | SFK |