I know an Indy in West End. He works from home, an ex VW/Audi guy. He uses genuine parts only and is trustworthy. Pete Taylor PM me if you want his number, its a home one so don't want to put it on the net.
Could give Kevin Parrington a ring. He runs an indy in Woking, just behind the Holiday Inn and his guys are german specialists (cars, not the language) and they've always been great for stuff I used to take down to them.