dewan does handle mini cooper maintenance, but they fair very badly in reliability, a family member has a cooper convertible in karachi and had done some research on the topic, he said most common issues were rattling timing chains, failed electric power steering pumps on the latest models, water pumps commonly leaked and the 5 speed transmissions are better than the CVTs. and easily damaged front radiator supports.
if you are looking for specific workshops than apart from dewan I cant help you in that.