If you can sell it privately not only will you get a better price than part-exchanging it, but it will also give you more bargaining power when you approach the dealer.
Also because it is still under warranty it makes it a good buy for any prospective buyer. So it would make good sense to save a few hundred pounds buying from you rather than a dealer.
Give it a try at say, £500 cheaper than similar models advertised by your local dealer, you never know your luck.
