Had a rear wheel cassette switched over, but the guy that fit it chucked the spacer, so the cassette was loose. Went in to get it sorted and the mechanic (who's name I didn't get) popped it in the stand, sorted the cassette and then found a whole host of other things wrong on the bike. He went about fixing the lot, talking me through what was wrong. I was back on the road in no time with a bike that felt brand new. Didn't ask for a penny. Highly recommended, great experience: the mechanic clearly knows his stuff, and was really friendly to boot.