Its all reassembled now, refilled with various oils and ready for the propshaft.
When I visited Dave Macs last week, they had been unable to build a new propshaft because those 2.5" CV joints have been out of production for years. The rear joint was ok, and just needs rebuilding with a new CV boot, but the front joint has a large "pit" in one of the slots that the ball bearings travel down. As an interim fix this is going to be welded up, and then ground back with a carbide cutter. Not perfect but it will work for a while, and the front prop is fairly quick to remove and refit.
If I cannot find any new CV joints anywhere, which is unlikely as they have all been used up, its a trawl through the various breakers to find 2 good ones, as they were used on Spitfire 1500 propshafts, TR7s and a few other vehicles. Long term I will probably have to have 2 made from scratch (expensive) as the angles of operation are too big for universal joints.
As to the diff breather, I finally drilled a hole in the top grub screw and brazed a piece of pipe into it, to which I have connected a plastic tube, which finds its way above the diff to the front of the engine for now. I'll see if any oil does drip from it, and if not, cut it back and form a simple U bend in it - to let it breath and stop dirt getting in.
I have not updated time and money in the last few months so the figures to date are now 1145 hours, and £23031
I really really hope it drives all right now with no more major issues, or it may find itself locked away in the garage unloved for a time.