hi whitey,
My Cooper S, also 50,000 miles, has also just been diagnosed with needing wishbone bushes replaced.
The dealer has quoted £340 for parts and 3 hrs work, and Lohen have quoted £390 for 4 hrs work but nicer-sounding powerflex parts
When I found my discs and pads needed replacing at about 40,000 miles, I replaced them with GTT brakes and kevlar pads, as it cost no more than having BMW do it with the factory parts. In fact, I think it cost a tiny bit less, but I've only just got round to doing the sensors
