I think I have already found the answer.

I was told that under the chrome channeling for the rubbers ontop of the side windows, and in between the gutter strips to the roof skin there should be a some sort of sealing compound. Aparently Mercedes used some sort of linseed based putty on the early models?
I will have to hunt aroun and find something available now that will do the job with out effecting the paint, I don't realy want to use silicon as if ever the roof needs painting again it could cause problems and is very difficult to remove properly.

any suggestions ?

cheers

(hopefully a much dryer) Damian