Well, from all my contacts with those three at festivals I've found them very helpful, and happy to have you play the instruments and ready to talk about them, and pretty knowledgeable about folk music. And I found the Hobgoblin shops in London and Crawley just the same. (I haven't been to the other shops, but I've no reason to think they'd be any different.)
Mind, you might walk out having bought a bouzouki or a mandolin, when you came in thinking guitar - but you'll be happy with what you buy I'll bet.