2006 Defender 90 TD5.

I have a vibration through steering and whole vehicle at about 25-35 mph. Vibration under acceleration and deceleration, But Most noticeable under engine braking. Dipping the clutch stops it. Other than the vibration between 25-35 it drives fine

Tried changing everything I can think of:-
All new polly bushes, ball joints, shocks, springs (2" lift), radius arms (front and back), A frame joints. New tyres (good ones), Wheels balanced, Wheels swapped round. Checked engine and gearbox mounts, checked exhaust isn't hitting anything under engine braking. No change - vibration just the same.

Only thing that has stopped it completely is to take the front prop off, and run in diff lock, which I thought pointed to the propshaft.
UJ all good in prop but New UJs fitted just in case. Vibration just the same.
Fitted prop backwards (just to try it) same vibration.
A spare prop fitted (appears in good condition) same vibration.

I have a brand new Wide Angle prop coming but i dont have much hope it will fix it.

Any ideas ?

would seem like the prop ,is it phased correctly for the lift,any play in the diff flange ,not rotational but up/down side/side

No play in diff or transfer flanges - sorry missed that one on my list of tried fixes. Flanges checked for play up/down & side to side. Flanges removed and new seals fitted to Diff and Transfer case.
Also forgot to say the new front radius arms are Castor corrected for 2" lift.

Props phasing. That is still as standard 90 TD5. Looking at them i would estimate they are 45 degree offset. Should that be changed for a 2" lift ?

I have a 200Tdi, with a 2" lift, no castor correction. I have a slight vibration (gets worse under load) which I believe to be the front UJ on the front prop. My UJ's are out of phase by 90 deg, tried 45 deg, which made it worse.
Sticking with what I have at the mo.

If you've got castor corrected front radius arms then this makes the UJ prop angle worse. Instead of wide angle prop you should try a double cardon but these aren't cheap. These are only generally needed for lifts more than 2" but every landy is different.
If your wide angle prop does work keep it well greased as the uj's are working hard.
Cheaper alternative might be to remove lift?