I went to stanton auto with a gearbox issue and they gave me a mobile number for a guy who works for a main dealer. Lives in maidstone and works from home but has star diagnostics and seems to get a lot of work. Gave me a quote on some work that seemed fairly reasonable
Talk to Andy. He has a wealth of experience servicing AMG's and everything else Mercedes.
Easy for you to get to, straight up the A21 in half an hour. He is very close to Orpington/Sidcup near the end of Sandy Lane. New clean premises and service better than main dealers. I totally recommend him.