Woking Motors at Walton on Thames are my local stealership so I avoid using them other than parts and for info
I take the MBs I've had (now an N reg E220 ) to CARLIANS in East Horsley - 01483- 28600 ask for Service and Dave the Service Manager, he's in from about 8 am. They are genuine and seem to care, prices are very reasonable http://www.carlians.co.uk/
Wouldn't buy a car from them again - but positive yes for service and repairs
I have heard that a place has recently opened on Kingston Road in Leatherhead (just North of the Plough Roundabout), not got any more info than that tho.
Also, just south of Surrey is IN Autos, near East Grinstead. 01342 844 343/ 0780 345 1281.
Trained Mercedes mechs who are very personable and seem to know their stuff. They recently moved to newer, bigger premesis, so they must be doing something right. They replaced the rear subframe mounts on my 190 and did it for the price they quoted & before they said it would be done, even though it was a particularly nasty job (the old ones were the most jammed in he'd seen) and replaced the shut-off valve on my injection pump as the diaphragm had split, the charge for doing this was minimal (like under a tenner inc part) even though I only asked them to have a look at it, I was more than impressed.
They are also happy for you to supply your own parts, should you wish.
Ask to speak to Ian, the owner, and tell him that Marcus with the black 190D that runs on veggie oil sent ya