Thanks everyone - I'd already sussed Coda and Guitar Village, thanks for the other tips.
As for World Guitars, they're just up the road from me. If PRS's are your thing you will soil yourself when you walk in there. Just loads of stunning and often rare PRS's, beautifully presented in a really cool old magistrate's building. It's very impressive and the guys who run it are very friendly and enthusiastic. I keep an eye on their website in case they get the kind of Gibson I'm looking for in stock, I'd like to shop with them on principle because their attitude is so good.