Mondeo tdci drive train gearbox diff whine

Hi , I was hoping you clever lot could help with an issue I'm having with my car?

I have a 2005 (55) Mondeo tdci 130bhp and 6 speed box. The mileage is 96000. In the last 3 months, I've had the DMF and clutch replaced with new thrust bearing. . The parts were L-UK.  I've also had a new aux belt and pulley kit fitted. 

Right, the problem....

About a month ago, I started to hear a slight whine from what I thought was the gearbox. Over the last month, the noise has got much worse. 

The things I've done so far....

I've had the car on a ramp with all 4 wheels unsupported. When up in the air, you can rev the engine and change through all the gears and it doesn't make any unusual noise, however the noise is very much there when driving through all 6  gears. In reverse, the whine isn't there. 

There are no oil leaks. Wheel bearings have been checked and nothing is apparent. 

I've spent approximately £800 recently. I don't really want to spend much more. 

From the sound, You would think it's the gearbox. What I don't understand is, when the car is up on a ramp and the wheels unsupported, the noise isn't there. 

Could it be a drive shaft or diff issue?

Any help would be very much appreciated. If I had hair, I would have pulled it all out by now. 

Thanks, Jim.