Since the Consimer Rights Act 2015
- this affects all purchases (including new & used cars) made by consumers on or after 01/10/15. It's a powerful piece of legislation and your rights depend on the length of time between the purchase date and the fault manifesting.
If it's less than 1 month, you may reject the goods out of hand if they develop a fault and receive a full refund. If >1 month but <6 months you must give the supplier one opportunity to repair or replace the goods (supplier's choice as to which). If this is unsuccessful then you may reject the goods for a full refund. Outside of 6months you have to prove the fault was present at the purchase date.
The only exception to the full refund rule is cars, where the dealer may make a reasonable deduction for the enjoyment an owner has had from the car. What's reasonable? Ultimately you negotiate with them or let the courts decide.
I used the above legislation to get our fridge replaced just before Christmas when it went wrong for a second time following a repair by Currys/Knowhow/whatever they're called today so it was very fresh in my mind.
If I do have to push The dealer for rejection then I fully expect it to be a long drawn out affair which will cost me dearly. However I simply cannot have a car that I can't rely on, particularly when I use it 30+ times a year to get me to the airport for work flights and my office is a 180mile round trip on the motorway.