All sorted, no big drama. It had spat all the teeth off 1 of the planet gears and another one had burst. Chucked in a 3.5:1. The nasty whine I had has gone, as has most of the vibration I had. Result!
Just ordered a Quaife LSD. Think I'll fit it to a 3.9 though.
The car feels a bit less lively now, but is better on my motorway trip to work. Decision decisions!!
Thanks for all the offers of help.
And for anyone who cares, RS2000 half shafts are longer between the bearing and flange so wouldn't just go straight on