With a main line dealer you should be ok, I've always got a reasonable deal and service from my Ford dealer. You should get a warranty and car fully serviced, you might get cheaper elsewhere but you've more of a comeback if anything goes wrong. They'll try and push finance on you, but you do right to reject. I've always found this site a good guide to car prices and trade in values so go armed with this info.
http://www.parkers.co.uk/car-valuation/ You won't get much off the price with a dealer, but walk away if not happy, they'll be in touch ! (and don't be tempted to buy new, waste of money). Say nothing about the gearbox, it's a dealer, they assume your car is crap.