The brakes work perfectly.

Been stamping on them and they are polishing up but the mark is still there. I think what happens is that the corroded bit then tears the pad material away allowing more corrosion to happen as the polishing pressure is lessened under that area of the pad each time the rust scale scrubs yet more pad material off.

The rear discs must be a different grade of steel because they have stayed bright and polished obviously with the same light use.