I couldn't see my own firmware in the list. Its stock 2.3.3 from Carphone Warehouse (CPW).

Its a 's5830xwkpy' but the CSC is 'cpwkp1'

I'm wondering whether there will be, or already is, an official CPW update to .4 or .5?

It doesn't seem like CPW phones are allowed (on Kies officially) to have other UK firmware regardless of service provider...