Apparently a new firmware upgrade for all HTC Desire S smartphones rolls in UK over the air (OTA). The new upgrade brings Android 2.3.5 Gingerbread with some new features including the Sense 3.0 user interface.
Like all the OTA updates local carriers will roll it in waves (stages) so if you get prompt for this update please report back to PocketDroid with comments down below! Did you get it?
If not you can get the deodexed version of the OTA build 2.10.401.4 firmware from XDA and manually install it (requires a rooted device and at some previous experience how to flash ROMs via recovery mode, clockworkmod).