Disco 2 Is it my diff?

Wondering anyone can help with my D2 TD5 noise problem. I have a cyclic woo, woo, woo sound coming from the rear axle area from sticking my ear around the car. It appears to be more pronounced when power on although it's still there when off the gas. Things I'm considering; wheel bearings, but I changed these last year and thought it would be more of a constant noise and it doesn't seem to change when cornering. Handbrake problem, again changed this a few months ago because of the noise and still there but the noise does sound a bit like a shoe is catching. Low diff oil checked and ok. Is it the diff that's on its way out, I don't know what a dodgy diff sounds like. Any thoughts advice much appreciated.

Others may come on here and tell me i am talking cr@p, but If you can feel any/much play, at the pinion flange, once the prop has been dropped, you will need to get it sorted.
There are a heck of a lot gears in there, all of which can wear.
One thing that can happen is that the pinion nut can come loose which leads to play and noise.
When I had this just tightening it up to the proper torque sorted it out and a DTI showed there was no damage to the crown wheel or the pinion.
But it you have had water ingress, then all sorts could have happened.
Dodgy seals can lead to trouble. As oil can leak out and water can get in.
What sort of life has it led? Has it done much wading?
A "hum in the bum" is something you have to have a bit of experience of, but it is noticeable.

Worth checking the rear doughnut between prop and dif. Even a few small cranks can make it unstable - I changed mine along with the UJ’s (gkn heavy duty option) on front and rear props and it’s made a massive difference to annoying drone that I had.
Have a look at discovery2.co.uk for UP’s write up- it helped me a lot!

What tyres do you have on? Are they in good condition?

Jack all 4 corners up, put the car on axle stands and get underneath. Should make life easier for narrowing the noise down.