I would heartily recomend Electrohill also. They seem to actually care about their customers. If I still lived in london I'd be there a lot more than I have been lately. The all time best shop for customer service in the west end had to be Allbang and Strummits, sadly no longer trading. Nice people, good gear, honest advice about anything and good prices. John Gold who used to run the place is possibly one of the nicest, most honest people I have ever met. I believe he's very high up in Fender Europe now, and deservedly so.
God, that all makes me sound really old :(