I took it to goodwins, my local auto electrician and they said its fooked!! Well it could be done but would cost more than its worth so I got another one. Fiitted it and all is now good.

.....Hi guys,first time ive posted,200tdi wouldnt start,did all the checks,the key jobby,checked starter all ok????...checked relay...fine......strange that alarm wouldnt set,no windows worked,no interior light,no radio...but all electrics worked and wouldnt turn over....so guys heres the fix;trace the live feed to the loom/fuse box,just before the servo under the bonnet,one thick wire is joined to 5 others in a very undignified fashion buried inside a "hessian sock"they were all corroded,2 had come apart completly,so cut back and rejoined and vrooooom....happy-disco-days again.hope this helps some unsuspecting disco fan.
P<S cheers guys for a fantastic forum.

Old post I know but it has been my saviour!

I've had the same problems with multiple circuits not working i.e starter from the ingition, internal light, radio, windows, I'd convinced myself that it was an earth issue with the earth being common to all circuits and have been going round in circles.

I found the post by cbeancnc about the "hessian sock" in the loom adjacent to the servo, opened it up and every connection was corroded with a couple being broken completely.

SO just a note to say thanks for the post it's save me a lot of head scratching!!!