I'm running a standard Cortina master cylinder with BMW 4pots and vented discs, everything still fits in behind the 13" wheels. No servo, braided lines and the brakes are sharp, think I was just lucky to get the pedal ratio and the piston sizes right.
Was good enough to stop my Mk1 when the previous owner had a 2.4 N/A YB in it, put the whole setup over into my crossflow powered Mk2