Ok I managed to get it the next day. I can't quite work out what the main difference in technique was, but when I put it back on, I left the hose off on the other end to get a better grip, and using the better available daylight I could see the mark on the nipple indicating how far the valve had been sitting on prior and it usually was coming up about 2mm short. After more attempts, not a great deal of force but perhaps a reasonable shove, it went a bit further with a subtle click. And then the giveaway that it was finally on: when the split pin was pushed down, it went down much easier, and once down, it could wiggle/rotate easily in place. (Before it was right as it was only partially in the groove or not in it at all.)
Also a big lesson I learnt when bleeding it, make sure the car is on very level ground. My car was facing a little diwn hill, and due to the nature of the split reservoir for brake and clutch, I needed the reservoir overfilled between each cycle. Spilt a lot of oil as a result of needing it so full but eventually got it.
Clutch is so much nicer now. Feels like it should. And combined with a clutch travel stop, am very happy with the new Sachs SRE clutch with DMF
(Engagement point is very high and travel stop is key)
Bookmarks