To be honest mate I think they saw you coming. You have to be very careful when you take your car to a main dealer as most are very unscrupulous and will always try it on by adding on extra costs and "bits that need doing".
I can't remember the number of times they've tried to lead me up the garden path with bogus jobs or being sat in a service reception, listening to the crap they are feeding the poor unsuspecting souls, especially women who often don't have a clue. I remember many moons ago taking my car in for a service and also mentioning that the front seats where a bit squeaky, thinking they could just put a drop of lubricant on the frame joints only to be told that the whole seat frames\assembly would need to be changed to cure the creaking which would have cost thousands! I politely told them to eff off. It's sad but unfortunately you have to be on your toes when dealing with them or they will take the p*ss.
I take my car to the dealer for basic servicing as I want to retain the FBMWSH but even then I shop around my local BMW dealers for the best deal. Anything else which needs doing and it goes to a reputable indie, at least I know they'll do it properly and not try to rip me off.