brake calipers

[Paul A]

I have a 63 plate J series, so it is what 21months old. I had new front discs fitted July 2015 - due to bad vibration under heavy braking. I now experience a rattle cum knocking from the front disc pads in their carriers. My garage says the pads are very slack, particularly the inner pads on both front wheels. Packed with grease the noise goes but as soon as the grease wears away they start to rattle again - sounds as if there is a serious problem with the front wheels. I am assured the problem is the brake pads being slack in their carriers. Garage have placed on order new brake pad carriers - will this resolve the problem? Annoyed to find that Vauxhall have two qualities in replacement part - after service parts and better top quality parts! Never had this problem of brake pad rattle pre the brake discs being replaced! Is it because of the cheaper version brake discs being fitted???