I have this exact same combo on at the mo, and they were a little rubby ounder breaking for the first few hundred miles, after a few thrashing sessions they have stopped now, can only hear them as slow speed with the drivers window open, the grooves cause a noise under breaking (you should have been in the car with the old discs on) that was noisy, but they never effected the performance of the breaking system. I understand your paranoia, im the same with noises from the car, but all disk and pad combos make different noises, depending on the depth of the groves, how many etc etc etc, i say if you have has it checked, dont bother wasting any more money persuing this issue, 3 garages can not be wrong really...can they! Stop driving the car like a granny, put a little trust in it and throw a few high speed stops at it repetedly, get it all mega hot and then see how you go...if the
problem still exists then maybe...do something about it if you can hear it over the radio.