Need a few more details to be sure? Colour/age/history/belts? For a late one, from a Renault Dealer, I can see you'd have to pay £5.5k-£6k to be fair. Whether that's a good price or not is open to debate - because you can get a tidy 182 for £6k privately now - although some people don't like buying privately which is of course their choice and is completely understandable. Also as you say, you want to trade in. How much are you expecting for yours - as the buy price isn't as relevent if you can get a good trade, it's the cost to change you really need to concentrate on. Ok so if it's £500 overpriced, will they give you a higher trade in than elsewhere?
Dan