If the job is done properly then I don't think £549 is too bad a price. Just price up the parts for yourself. Parts alone must be over the £200mark, and the VAT sticks a whack onto it.
I know its not peanuts when you have to go out and earn it, but some garages would charge you that for a "change the oil and kick the tyres" type service..e.g. Mercedes
Have I told you about the official Merc dealer who rang my brother while it was being serviced to tell him his 190 would need all the diesel filters changing, and it would be an extra £150. My brother said "You are the experts..do what you see fit"
When he was presented with the £1200 bill (I joke not) he pointed out that it could not possibly be his bill as it contained a number of diesel items. "My car has a Petrol engine"..he advised the so called "experts". He received a somewhat lower bill and never used them again.