tbh, I'd rather go into a small specialist record shop but then again there is plently of choice in London in the stripe from Soho up to Kentish Town - all pretty close for a days quality record shopping. There is more of the scene there. DJs you see out at parties, flyers for undergound parties they would never advertise in bigger stores.
The answer is listen to alot of music and to use a wide range of stores to find the perfect tunes for your sound. I personally always run of out money before I run out of quality tunes I can get.
that said if I lived in Hull, Leeds, Plymouth, Bristol, Newcastle... I think that a large quality independent with 6 or 7 specialist vinyl areas in one place would be really good but is anybody gonna take the risk? When you start getting cross-genre it definately becomes more of a business than for the love of it. Larger stores need more staff and you loose that indepth knowedge you get in small stores.
The internet provides some good opportunites to sell to audiences that aren't near you but then that becomes transaction - something people will shop around for. Small shops, face-to-face with the people who know is definately the best way to buy.