In reply to James Malloch:
You'll have the below text from MSmarket already perhaps. Rejection is the way to go here, with a deduction from the purchase price for the use he's had of the car.
I rejected a car after 9 months (endless ECU issues) and got £5600 back from a £6500 cost - so not perfect but better than being stuck with a lemon.
You have a right to reject something faulty and you are entitled to a full refund within 30 days of purchase in most cases.
After 30 days you lose the short-term right to reject the goods.
You’ll also have fewer rights, such as only being able to ask for a repair or replacement, or a partial refund.
In fact, you’re legally allowed to return it up to six years after you bought it (in Scotland, it’s five years after you first realised there was a problem).
But it gets more difficult to prove a fault and not normal wear and tear is the cause of any problem.