I've trawled the internet, had various mechanics look at it and finally found the problem. So I thought I'd share it in case you haven't heard.
The problem: Press the clutch when the car is cold and its hard to get into 1st or reverse and there is an odd rattling noise, sometimes as you lift the clutch but always when pressed but amazingly disappears when the car is hot. Even in neutral. Many theories by mechanics (such as "its your thrust bearing" - no its not coz it would rattle with no pressure on the clutch - but always "Ah, all Discos make that noise. Nothing to worry about"
Well turns out, yes it is something to worry about. The problem is the spigot bush which costs 50p ! I had 2 clutchs (plate, cover and thrust bearing) and both times the rattle went for a week, only to return and only to be told, "Ah All discos....." yes yes yes.
Next time you change your clutch, tell your mechanic to change the Spigot bush. It can't be inspected (like my last mechanic said he had) unless you take it out an when you do, you'll find its either in pieces or well worn and making your dual-mass rattle away causing it some damage. Turns out it is one of the commonest causes of failure of the dual-mass and doesn't do the rest of your clutch any favours. If it rattles, change it, don't just grease it up