Hi all,
What shall i try next? I have a 1991 LR90 with the 2.5TD (19J) when the engine is under load in 3rd gear upwards the car makes a horrific squealing sound. It sounds like a fan belt but i have replaced the fan and power steering belt, all pulleys felt okay. It doesnt make a noise if i rev it in neutral though. Can a release bearing make this noise?!?!

Release bearing just sits there doing nothing until you depress the clutch pedal with the engine running so it isn't that. Try driving it briefly with all the belts off to eliminate stuff.
You may have the wrong belts/too slack/worn pulley or less likely, water pump, alternator, power steering bearing issues. Removing belts will help identify which.
Might even be a prop UJ breaking up.

Get the phone to capture the noise and post it here.