| wether this is the same for mini, but BMW have an AUV warranty. If they cant rectify a fault within 30 days they wil give u another car.
Asking for a refund of a car after 3 months may be a tall order, and something I dont think you are entitled to sadly.
I would write a log of all the issues and their timeframes. You need a good pattern of events all listed, then write a letter, be polite and try not to be rude etc.
State the repair, what you want, and that you are doing the honest thing and giving them a chance to rectify the situation first. If they do not provide satisfactory resolution, you will take it the next step to trading standards and MINI head office.
One stage at a time, sometimes these disputes can be drawn out!
good luckk | 
