Just thought I'd do a little update of where we're at now, JIC it helps anyone else.

I think the intitial problem was a pain issue. Maybe left over from her needles or from the nappy rash. Whatever it was, she doesn't jerk awake anymore. She is still a little hard to settle, but over the past couple of weeks I've been learning a lot about her personality.

First, she is very easily overstimulated. Just a small outing can unsettle her for a full day. I discovered this because she always slept well on Saturdays - because we didn't go anywhere on Fridays.
Second, she has a very short sleep window. If I don't act with the first tired sign then it can take ages to settle her. She doesn't do overtired well, lol. But if I act quickly, she can sometimes self settle.

So, we have been very slowly improving things, I'm actually getting a 4hr block of sleep at night. Hopefully things continue to get better.