MG Car Repair: noise never heard before, wheel bearing, gearbox

Question
never heard this noise before, sounds like a wheel bearing but isn't and it's not gearbox (had specialists listen) either only happens at 40 - 50mph.

Answer
Hi Doug.  I need more information.  What car are you driving?  How loud is the noise?  How do you know it isn't a wheel bearing?  Where does it seem to come from?  Does it only happen with the overdrive switched on (or off)?  Any particular gear?  What happens if you dip the clutch?  What happens above 50mph?

Have you done ANYTHING to the car recently? (for example, fitting a new gear lever gaiter)  The reason I ask is because the chrome surround has 4 screws and one is shorter than the other three.  If you fit a long one at the front it can just touch the gearbox and cause all sorts of strange noises which come and go as the engine flexes on its mountings.