Thanks for your help Muskie and John. ......The second 'spacer' was actually the outer ball race Muskie, so that sorted that one.
In the end I split the cases with a pair of spring compressors for car suspension. I unscrewed the claws and put them back on so they face outwards. Using the outermost barrel studs to push against, and inside the sump, the two halves slid apart beautifully.