Well, BeoWorld isn't really the place for flaming engineers - but £600 for a check and lube is a bit, ummm, OTT ?
Upon looking at his website, he claims to have 40 years experience and appears quite knowledgable. I would certainly double-check that he has understood exactly what you want him to do - i think with that level of experience you owe him that..
I'm trying to defend someone here that cannot answer for himself, but maybe he gave that quote because he doesn't know/understand B&O perhaps as well as he claims to, or perhaps he has the wrong impression of what you require?
Personally, if you're in London and have genuinely been quoted £600 for a check and lube, i would call Simon Harry at AVA Services. No conflict with 'other resellers' either - we all use him, he's a great guy and a B&O genius !!!
Lee
BeoWorld - Everything Bang & Olufsen