Best price I found around my area (10 mile from UB6) for brake fluid change was Scotthall Ruislip. They're changing the Z4 and also 530i both for £91.95 each all in.
Changing the zed on wednesday, so will report back then.
I thought you had bought some Si calipers for a brake upgrade? Or has that been done already? Probably just behind the times. Wondered if you were putting those on and changing the fluid at the same time. That was my plan... if the final carrier ever arrives!
