If I need anything done in future I think I'll go to the VW specialist around the corner from my office in Cirencester, good guy. I was in the middle of meetings when they called with the list of things so I was caught a little off guard sadly, given 5 minutes to think I'd have declined any extras. Live and learn I guess... I'll call them when I finish work today but not much I can do about it now expect!
No, probably not much you can do about it except to make them aware that you now know full well that they conned out of money for doing something that didn't even need doing, and to tell them that they can expect never to see you back there again. Dealers who try to take advantage of or lie to someone who they think isn't technical don't deserve to be given any business.