Salient points:
- A deep or low whirr whirr sound. Not loud, not resonating openly. You feel it in the seat of your pants as you drive.. I guess.
- Doesn't change with speed, direction, gear or whether clutch is engaged.
- No knocking or looseness when rocking rear wheels whilst on axle stands
- No roughness when rotating rear wheels
- Bearings greased in the last month
- CV Boots intact and not torn
- I have just removed right side Drive shaft. CV joints have good clean grease. I am currently cleaning and greasing them
Hope to finish CVs tonight / tomorrow but based on what I see this is not the cause.