I could help if you were buying in the US but not in the UK..sorry..If it were here I'd tell you to find the loan value, blue book/nada/ retail value and research the invoice price the dealer paid for the vehicle. This will give you a better idea of where to start negotiating. After that make sure you check multiple dealers. It always helps to have guys competing for your business. If the vehicle you are looking to buy is historically known for dependability than I wouldn't get the warranty but to each his own. Car sales is a high pressure market in the US so it tends to be a buyers market. Not sure what its like in your neck of the woods.