Hollow Roar noise from front - HELP

[NICKM]

Hi all
I'm expereincing what I can only describe as a 'hollow roar' noise from the front of my new E70 (275 tyres front & 315 on rear)
The noise seems to be at worst around the 20 to 60 mph and different roar sufaces make a slight difference to the noise, but its always remains in the background.
I took the X5 back to the dealer last week who checked it over and found no fault with bearings etc..etc... and they also test drove an identical model they had which was making the same noise - so they put it down to tyre / road noise !!!!! MMMmmmm !!!!!
Has anyone else experienced this on their E70 ????