Thanks guys. My car has been outside of the BMW network though since I bought it (for servicing etc.), so I guess they would not have had the opportunity to "advise" me at any point. It has been regularly serviced though, but by an independent mechanic.
BMW will still get the parts sales though as the specialist I am using needs to order the fuel pipes, and also suggested a MAF sensor. From other reports I've read this seems to be prudent to change the MAF also.
I have made the decision to go with an independent BMW specialist who has quoted me a ~30% of what BMW were originally asking for.
Sheila, how long did it take for you to get an agreement from BMW?