My good friend Nuno, i'm also having this problem as you know...
It is a sort of a "clunck" when i brake at very low speeds...
However, the problem as become worst...most of the times i hit the brake pedal..there it goes that same noise, now at any speed and "clancking" twice..
I went to my dealer, they checked it and i was told i had a gap in the brakes...in the leftback wheel..but they didn't know why.. however this was previously to getting worst..
I have the JCW
brake kit however..
Anyone with the same problem?