Hi Crossy,
thanks for the quick reply! I thought the whole point of Land Rovers was messing about with nuts and bolts and getting dirty!
Seriously though, the original rear axle made the same grating noise and eventully the diff blew up in spectacular style punching through the axle casing! I completely rebuilt another but the same noise is there leading me to believe it may be the prop(s). I'm certain it's not gearbox as I had that professionally overhauled (at great expense) before refitting. The fact that the vehicle is fine when laden also leads me to think 'propshaft angle'.
Regards,
Mark