Thanks Achim,
I believe I have managed to work it all out now, The issue was the sequence of the assembly, I assembled it last night without any grease just to see if it would work and I believe I have got it all correct. Putting the ball bearings back in the worm is the hardest part. But I am a clock and watch repairer by trade so this isnt too bad...
Over the weekend I shall re-assemble with bearing grease and see how it goes.
I do have a big blue book workshop manual on old mercedes cars but didnt think it had much detail on the power steering box. I best check and read it ...
Regards
Steven