Sold a defective car and refused refund

JDC cars in Malmesbury sold me an A Class Mercedes with the express statement that they never sell these types of cars without first re-doing the gearbox. After a test drive I paid cash for the car and received the car with a road worthy certificate. Once I got it back to CT, my mechanic pointed out that the brakes were almost gone, the brake sensors had been DEACTIVATED and a headlight was blown. I found out later that the gearbox had NOT been done at all. Long story short, the car shouldn't have been given a road worthy certificate and the gearbox was and still is ******ed, even though they took the car away for !3 weeks! for repairs. No courtesy car was offered and when I asked for one, they refused. When I had it tested at a gearbox specialist, the same problems were there. DEKRA Malmesbury gave the RWC and I have to suspect that something funny went on since it should never have passed. They are refusing to refund me as per the CPA regulations and I now have to sue them. In my experience and opinion DO NOT BUY FROM THESE CHEATS! DO NOT TRUST Road Worthy Certificates from DEKRA.!