If you bought the car from a dealer or trader, you will have strong grounds to argue this serious safety fault was present or developing at the time of sale. As a result, the seller should repair the car or (if the car can't be fixed) offer a refund (minus a fair deduction for the use you've already had).

The 2015 Consumer Rights Act doesn't apply to private sakes, but the car must be road-legal, safe and as described. I think the previous owner would have a case to answer, along with the MoT station that passed the car. Your garage complaint should be sent to the DVSA.

For your consumer rights, see: www.honestjohn.co.uk/how-to-reject-a-car-your-cons.../