I got mine from DMS last year but I think they might have stopped stocking these now. I know Steve Webb Models in Frodsham used to have these in aswell, perhaps a pm to Matt Dodd would let you know if they still stock them. If you do draw a blank on the UK shops, there are tons of them available on ebay and through other web stores in the States and in Asia. Personally, I love 'em and am gutted I didn't have mine ready to race in the National this weekend. There are tons of hop ups available and the cars themselves are really strong (after you do the GB02 front end). The bits are cheap and they look (IMO) cooler than anything else available.
Second thought, why not just call Steve Webb Models tomorrow instead of asking Matt now!