A6 Front end noise

[DontTouchWilma]

My A6 has developed a slight vibration and noise from what i think is the front left. its only really noticable at motorway speeds, sounds like a drumming noise, and the vibration can be felt through the car but not the wheel. I recently had the tracking done and its almost perfect, ie it doesn't pull to either side. The front brake discs are rather warped, light braking and the wheel judders, heavy braking and the judder isn't so bad. I also recently put a set of 18's on the car, though the problem was there before the wheels went on.

I thought it might be a wheel bearing away, but there doesn't seem to be any play in the wheel if its jacked off the ground. I'm at a slight loss as to what it could be, is it a bearing away, bush away, the warped disc rubbing the pad and causing the vibration? More importantly, how do i fix it?

Any suggestions much appreciated

Mark