I believe every query should be resolved for the sake of the next "worried of Bristol" who uses the search feature (not that enough users do I think)
The problem above was resolved as follows:
I measured the shaft from end to pinion face and gave it a smack with a copper hammer then measured again it had shortened (moved inwards) by .010" this encouraged me to try again and another .015 moved and a gap showed between the crankcase half's. continuing the process in the end the movement was sufficient to fit a standard two leg extractor and take off the pinion and split the cases. So it seems the key is common to both pinions and stays on the shaft in extraction.That is, I believe the undocumented procedure.
Incidentally the flywheel end was an easy knock out the double bearing did come out with the crankshaft I will leave it in position and Alpha can get it off. Now to find a suitable box...
The whole engine strip took a lot longer than I expected now the wait is for the spares service to reopen I have a long list.