Good tips Annette thanks. After plenty of trying I've finally got it to hook up. (It's difficult to see exactly when/where the needle co-incides with the rotary hook because other components block the view). And when you do get it right, the grubscrews that hold the rotary to its shaft are around the back - inaccessible! Anyway I got it in the end. It remains to be seen how well!
Fun? Yes, also the rotary contraption needs to be positioned correctly laterally along it's mounting shaft too, otherwise the needle scrapes against it. Quite fiddly, but I think I got there. The bobbin thread is picking up, and the machine is doing a passable stitch (even if it is turning by hand because I don't have a footpedal to power it).
Cheers Annette.