There are several listed on our USM Club card. Century. Heads Up, Mollie & Co., and DDM depending on your location. My R52 is currently at Heads Up Automotive in Spartanburg getting a 100,000 Mile service on the Supercharger. They also serviced my brakes quite a while back installing new rotors and pads.
Thanks to all who replied about possible Mini service shops. We had the rotors and pads replaced at Mollie and Company and was pleased with the service Dave Cathey provided. I also definitely recommend Mollie and Company as an excellent service provider.