From that info it looks like the discs have developed Cementite over the whole face (the pictures show only one part, but it is like that 360deg), or like Mike said the pads have left deposits all around apart from that first 1cm, which I guess may be the coolest area?

I've had the 'pad imprint' problem before on an A3, you could plainly see it and the high spot was noticable all the time through pedal pulsation, even cold.

I now think what has happened is that the disc warps due to the different properties of the cementite against the normal iron, but on cooling the disc returns to within tolerances. So nothing to do with the Brembo calipers. *awaits 007*

Obviuosly you cant see a warped disc by eye, unless the pad imprint is present, but you can generally feel it by spinning the wheel and listening, or just through driving. My discs are fine when cold, warped when hot - that's why I thought it might be something else causing the problem.

So thanks to the people who contributed, it looks like the problem is solved.

Mike, cancel that order for the AP's, I'm getting some 60 quid special discs

Only joking BTW the order remains on!