Help, is it gearbox?

Have a 54 plate Titanium x 2.2 TDCI with 45k and have a wheel bearing like noise on the passenger front, the noise has got gradually worse over last 4 months and is at its worst at about 40 mph and can only be heard on the smoothest of roads, there is also slight vibration felt thru the floor of the car nothing thru the steering.
I have put 2 new tyres on front and no change have also replaced the bearing with no change.
I would appreciate any comments as the warranty runs out on 22nd April!
Thanks.