spitzy

Hi to all I'm after help please...i have a 300c CRD 2006, had new pads and discs fitted.Basically the car is fine around town but on the motorway after about 20 mins i'm getting severe wheel wobble on braking ...i have to bring the car down to about 40mph.On stopping there is an awful smell from the wheels. I've had all the discs replaced...again...still the same..i'm open to all ideas please help me !