One last question then. I am now aware that the TC will need to be swapped out to get the 4Matic working again. Nothing else will work as far as I can see from reading the posts above. So, how difficult is this to achieve? Can it be done with the transmission in place? Any difficulties? Any special tools required? After swapping it is then the case that I wold have to hope none of the electrics are still at fault. The car is cheap but if the swap out is to difficult then it will not be worth the effort. There appears to be plenty of TC's in the UK from scrapped vehicles though of course the question then arises whether they work or not.

I am assuming that it is not the lack of fluid caused by the leak that is the problem but the innability to achieve and maintain the correct pressure to operate the clutch mechanism.

Thanks for all the help it has been more than useful in understanding this.