Thanks for insights, everyone.
I have been referred to an obstetric physio, but all she did was look at me, give me a belt and crutches, tell me to do core stability Pilates exercises (which I always did anyway - I have a good core) and then she referred me to hydrotherapy for some silly resistance exercises, which has made things a lot, lot worse. She didn't lay on hands and do manipulation at all, which I find a bit worrying. I have made a formal complaint to the Chief Exec of the hospital, btw, as this is part of a long saga.
I have had some private chiro which means I can walk a little bit with crutches. If it wasn't for that, I don't think I would be walking at all.
I'm officially disabled now and can't imagine ever riding or skiing or hiking again myself, or indeed doing anything fun, but I really hope I do get better.
My heart just breaks for herbietea and I wish I could do something to help. What a desparate situation.
I asked the physio about recovery time and she seemed to think I would be better straight after the birth. Now I think that's a bit unrealistic. Nothing else gets better straight away so why should SPD be any different? It's interesting to know that even with just a few posts, people's experiences seem to marry up with what I would have expected.