Well, there's been an unexpected turn of events here. Contrary to the guidance not to do CC in the mornings that I've read, we gave it a try, due to DD waking at 4 yesterday morning. DP went in and lay her back down, she screamed furiously for about 45 seconds and then stopped and went back to sleep. She then woke at 5 and 6.15, but with no crying, just grumbling. At 6.30 we got up with her.
This morning she started chatting happily in her cot at 5, fell back to sleep on her own, did the same at 6, and then 7.15. We got up with her at 7.30. Bloody amazing. We did the outside time thing yesterday, but I think for us the CC [if you can even call it that, 45 seconds of yelling] had the biggest effect, as she still woke early, but she wasn't crying and resettled.
We'll see what tomorrow morning brings, obviously one day doesn't make a pattern.
It reminds me of when she was about 6.5 months, and had gone through a v brief period of needing to be rocked to sleep. We had continued doing it, but it had stopped working, she was getting really annoyed and wriggling, rather than being comforted by the rocking. We tried CC with total dread, as we were really against it, but she never cried longer than about 4 mins, and only did that twice. She was also crying angrily, rather than sadly, IYSWIM. Anyway, that totally did the trick and she went back to self-settling fine.
Sorry about the long CC ramble, my point is that both at 6.5 months and now, neither she nor us were happy with what was happening with her sleep. She was much happier yesterday and today after longer sleep, and the result was the same at 6.5 months. I think DD sometimes gets into a habit that isn't helping her, and CC can press the reset button, IYSWIM.
We'll see. Of course I could well be posting here tomorrow about a 4am waking. 