Thanks Jon, you have mail on that...
Well, I got away fairly lightly today which was nice!
Had an 'intermediate' service inc new oil and filter etc, got gearbox oil changed, replaced some vacuum hoses somewhere (thats what the dropping revs was) and cleaned the car all for £240.
And the whining diff has apparently been caused by me using the DCCD on tarmac!
Now Ive heard / read many thoughts on this and found the consensus was its ok when wet/slippery etc, but Paul almost gave me a bollocking for using it! He was adamant that its only for driving on gravel etc and I should only wind it up one notch if conditions were very very bad, and then one notch only!
The most I have wound it up is 2-3 notches in the wet, but thats all...
Strange how there can be so many different thoughts on it.
Also enquired about the gearbox rebuild, he said between £600-900 to include pulling it out of the car, sending it away (to Bill Gwynne apparently!) new synchro rings and full rebuild, sending back and reinstalling to car.
Think I'll wait a while longer then!