America - when the £ against the $ was better. (my G&L bass)
Otherwise: here (several basses, Trace Elliot stuff), online retailers like Absolute (leads, mixer etc), Ebay (odds and sods like strings) and Andertons in Guildford, Surrey (Yammy bass and Warwick cab - great store).
There is a big guitar shop in my town but they're so aloof and overpriced, that I've stopped going in there.