Shaft replaced 300 miles ago and I'm pleased to say the problem has been solved:)

Thanks John366 it turned out to be the double universal joint at the front. Too far gone to rescue, probably because it can't be greased, but at least I know what I have to deal with now. Sourced a complete shaft from the breakers for £75. Should be fitted by the weekend. Fingers crossed.

The noise doesn't seem to come from the engine. Tickover is quiet and and it stays quiet if revved in neutral. It only happens when applying drive on a low throttle. Lift your foot off the gas and it goes quiet, give it a bootful and it goes quiet.

I have a disco II V8i ES and it runs very well but on gentle pull away or applying a little extra gas at cruise I get a sort of chirrupping squeal. It doesn't happen if I give some welly either at pull away or on the move. Anyone got any ideas?