I bought a used approved R-Class from a big Mercedes-Benz dealer around 16 months ago. The car has had a history of problems from the time I purchased it i.e. steering wheel issues and suspension problems. Most recently, it has been in for repairs for well over a month for faulty air conditioning (new compressor was hard to find and, when found, it failed again because of a blockage in one of the pipes). I had extended the warranty for a cost, so the works have been covered and they have provided me with a loan car. I've asked for a refund on the basis that I believe this car was not fit to be sold as used approved given its history with me. They have not accepted but would be happy to review the figures if I were to part exchange for a different vehicle. I have not asked them what those numbers look like yet. I would just like a refund. What are my options?