Hi, a few things can happen here, cracked disk, Brake Pad retaining spring dropped off causing the pads to rattle, If poss SAFELY jack up the front of the car make sure it's in Neutral, select any gear & ask someone to brake with you at the wheels to detect which side it is, then remove the road wheel and check what has been stated.
That may be TWR and I have always wondered about some of these franchises as they often seem to find problems that never existed. But I believe quickfit now do MOTs so they must have some mechanical experience?