Have a noise above 35 / 1500 RPM , a kind of "Waaaa/ wapa wapa" deep drone that changes with speed , wheel bearings have been checked - no fault found and replaced just incase but the noise is still there , engine noise is normal and the drone doesn't change with engine speed. WTF can it be !! Car is a 2.0 Auto.

That's 35 mph/1500 RPM. Nothing below that.

Saw toothed rear tyres?

They are spankers , wife's old A3 had buckled alloy once that did something similar but I'm not convinced that's it in this case

Discs are another possible cause but they would have had ample inspection presumably when the wheel bearings were changed. When did the noise start and what else had you had done to the car at the same time?

Other thoughts? Something loose in the engine bay or underneath like a plastic undertray? Does it stay the same if you open the windows?

I test drove a 2010 estate that made a wailing noise at 40 mph. I thought maybe a wheel bearing at the time, but I think it fits the description of sawtoothing.

Does it make noise if you coast above 35,or above 1500 rpm in neutral?

No sawtoothing , last Vrs had it bad, noise apparent whilst coasting in Neutral. Revs and mph need to be together for Noise.