Well get a quote from them before you agree to any work!
I turned up at thier garage and I asked them simply to quote supply and fit a diesel fuel filter on a 320D should be a quick and simple job they quoted me 4 hours labour to fit @6.00phr!
Sorry, but if you want to take four hours to change something that takes less than 10 mins max for a competant person to do then either they are clearly inept or masking a low quoted hourly rate. Clearly, this is not a reasonable amount of time to carry it out.
It's a shame they tried it on as i had alot of work to put thier way!