Buyers rarely pay the advertised price for cars and will usually expect to haggle. If you're dealing with a trader, you'll have room to negotiate or get a bit more for your part exchange. Failing that, ask them to chuck in a warranty, mats or other features you fancy (GPS, window tint). Private sellers are also ripe for haggling. Try and secure a better price for the car especially if the tyres are worn or the road tax is close to expiry