Thanks for the advice, Gary!
Yes, I am running OEM brake fluid, and it sounds like my issue is much more a case of fluid boiling - I didn't notice much loss of "bite" as the pedal got progressively longer.
Will a higher spec brake fluid be noticeable to a dealer? If so, is it likely to affect my warranty or maintenance contract?
Also, any idea what would trigger the brake & DSC warning lights? Is the car detecting excessive pedal travel perhaps?
2008 Alpine White 135iM, High gloss black / satin chrome trim, Xenon lights, Hi-Fi sound, ext. lighting package, BMW Performance wheels, side skirts, pedals, gear knob, exhaust, high gloss black grills, carbon mirrors, carbon decklid spoiler, 35% security laminate, Tii graphics