At last I've re-sealed the spare transfur case. The first problem was there are different sizes for pto seals and the one I bought was too small for the holder on this case so I had to rob one off a spare pto. I used spedy sleaves and a two part epoxy steel to cover the groves in the flanges.
My aim for tomorrow is to swap the transfur cases, install the new handbreak and if all goes well re-seal the back of the gearbox.