VirginVWman: If you've rang VW for a settlement, don't forget, that's a now settlement, you'll have probably shaved another £1500 capital off your settlement fee by March if you were ordering now for then. In March then, you'll owe about £16000, so £18000 p/x achieved is £2k equity (you could achieve that with my dealer no doubt, as I got £18500 for mine being 5 door). Add in your £3817 Orangewheels discount (I added in the discount for your leather and white paint) on 3 door manual, white with leather @£31875, and you should be at the equivalent of £5817 down as deposit, financing the other £26058 @ £358pm according to the solutions example following configuring your spec on the website (GFV=£18044, but that takes no account of your leather - expect £300 back on that).
You don't (usually) get a great deal both ends - a realistically low p/x for a heavy discount on the new one, or almost sticker price on the used lot for your p/x and nothing off the new one. Most dealers are happy to fall somewhere in between, giving you £2k less than used sticker price and maybe £1000/1500 discount on the new one so you feel you did alright both ends. If you stood your ground for £18k part ex and full Orangewheels discount, that's probably realistically achievable. Chester VW are looking to buy your p/x blind, on the assumption it's close to mint (and will still be in March), they should be persuaded to give you £18k to seal the deal, knowing full well they'll have it up for £22k then.
