Is it a wheel bearing?

[Gazza450]

So I used my 2007 V8V for a 200 mile round trip this weekend and the car ran fine but on the motorway I became aware of a "drone" or rotating noise from behind the rear bulkhead which at 70 (+ish) was actually louder than the engine but I can't actually define if it comes from on side or the other. I am hoping it is a wheel bearing but am concerned it could be the diff/transaxle. It has new Bridgestnes so It's not a tyre issue. How can I identify what it is likely to be? The car has only done 32k miles and has a full Dealer service history so all fluids have been changed as required. Any suggestions or ideas?

[Gazza450]

Thanks for the quick response. I am away all week but will get it off the ground next weekend and see if I can find any movement. I'm not aware of any weakness in the transmission so hopefully it's wheel bearings. Any thoughts on what they cost to replace?