it's been a while since i've had to upset a trader by quoting pieces of literature from the oft. i'm not sure either about the cost of returning the car. when you buy stuff online and its delivered to you and faulty, the trader must cover the cost of return, but (obviously) when you buy from a shop and its faulty you have to take it back to that shop, which is probably the same situation here.
again thinking back to smaller purchases, you should send the trader a letter highlighting the problem and stating you want a refund. give them a timeframe to respond to, perhaps 14 days. i think you have to give the trader the opportunity to rectify the fault, but then again as it's only one day you may be entitled to refuse a repair and just have a refund. if the trader won't play ball, you will likely need an engineers report. the trader may request this anyway. if the fault is one that can be proved to have existed when the item was purchased (no trouble there), you can claim the cost of the engineers report back from the trader. as i said, check that forum out, there's some great info. some of it will surprise you.
like this. did you know that if you buy something online and you change your mind (within 7 days normally), the shop cannot insist on it's return before they issue a refund. they have to give you a refund within a reasonable time (30 days) whether you keep the part or not. of course, they can then take you to small claims court to get their item back, but they cannot legally refuse a refund.