Did you ever find the cause of your noise? My focus sounds like it's doing the same thing. I get an odd noise over 30MPH and it's more pronounced when the steering is turned towards the left left. I'm thinking its coming from the drive shaft, if I coast in neutral and steer left the noise is not so bad. Doubt it's the gearbox, there is no vibration on the steering or gear level. Road noise tends to cancel most noise out over 60MPH.
Have to say, I completely forgot about the problem. Soon after I got the car, I did take it back and it had the front bushings changed, and to be honest, that might well have been the resolution.
The other problem is that I did have a tiny tiny break in the mass air flow hose, found it after I replaced it so I suspect this would have been a contributing factor. Unfortunately the oil on the hose actually hid the break...
Had mine sorted yesterday, front right wheel bearing was on its way out.
I think there is an alternative issue that may be playing part in the noise... The infamous split pipe in the design of the intercooler intake pipe...
I need to replace it at the next weekend with good weather and will let you know the outcome.