Sweet have ordered some new parts from BMW!
OEM CSL front brake rotors (345cm instead of 325 stock).
CSL carriers for bigger front rotors
OEM CSL rear rotors
Edit: I'm already running OEM CSL textar pads, which have heaps of life left in them.
Aftermarket stuff I've also ordered (it's not all OEM, but then again neither is the aero):
Goodridge braided lines
Decent Motul brake fluid
I didn't order the rear calipers (with the slightly larger piston) in the end. They were really expensive, and tbh I doubt I'm a good enough driver to notice the minute change in bias.
Next up: new 18in tyres, then maybe replace shocks. I've also requested prices for CSL front and rear swaybars (both are uprated over original M3 ones 30.8mm and 22.5mm respectively).