Wheels In Motion recommended on Mercedes forums also, it's difficult to get people who know what they are doing. I have a Mercedes C124 E220 (the last properly built Mercedes) and I have found a mechanic who I can trust locally, I liked him as when I rang with some problems he was prepared to talk for 15 minutes on the phone honestly about them, he then fixed them and looking over the car found stuff that had been missed on a £180 car inspection!
Maybe I'm just getting old but I seem to come across people in all walks of life who just are not any good at their jobs.