[dave1712]

For several P/Xs I have used London Camera exchange (stores UK wide) and Camera World (mainly London area) and have been very happy with the service. Like all good retail stores they have to make a living and give a warranty on used goods so if your looking for max price for yours and min price for the one your buying then sell privately and buy from a discounter. I have found that by the time I factor in ebay + paypal commission (13% or total receipt incl postage) then the difference for p/x with a reputable dealer is not so great - plus its sell it and forget it.

Also haggle, and If no joy on price then ask for a spare battery or a camera case or similar that is useful to you and doesn't cost them much. Good luck!