I would imagine that you would make much better money selling on here and then just buying your camera from where ever you like. If you're talking about part ex then you are limited to deals available through that retailer. Have a look on camerapricebuster, see what the best price is for what you want. Find out a price for your kit 2nd hand on here, I think you'll find you'll keep more ££'s in your pocket that way, rather than doing a part ex through a dealer.