Mystery Noise

[Lagotto]

2006 CR-V 2.2 CTDI EX 115k miles. Ive got some pretty bad noise both at tick-over and driving, only when Clutch Pedal depressed. My recent history is new Master/Slave Cylinders, fluid flush, no change. Suspected DMF/Clutch, so all changed. Problem exactly the same. The DMF/Clutch replaced again on the suspicion of a faulty part. Problem exactly the same.
Now the concern has switched to the Gearbox input shaft bearings. Does anyone have any ideas or experience of the possibilities of it being the gearbox? Apart from the noise, the car drives extremely well, smooth and faultless, but the noise when driving, only when depressing the clutch pedal to change gear, is pretty bad. Once the clutch pedal is released and gear change completed the noise is gone again.