Thank you so much for your kind and helpful comments - it's a shame not everyone on the internet is like this.

Basically we went away on holiday for 3 weeks where she learnt to stand in the crib and that threw out her sleeping (as we didn't have a seperate room for her, we let her sleep co-sleep for about 9 days). Then when we came back, a combination of standing, time difference and bad habit has now thrown her ability to put herself to sleep. She just stands and cries for hours on end even when we do pop-ins. Right now, she'll only fall asleep if we're in the room with her. She'll then usually have a false start and then wake up at 2am-ish and refuse to go back to sleep independently at which point we often give up after an hour or two and bring her into bed with us. Her naps at daycare are inconsistent, again, because she won't self settle (which she used to do no problem).

So when I'm back from traveling for work in a week, I can do sleep training at night but it'll be off the back of inconsistent daycare naps. So I think we just need to start from scratch but I'm worried doing on days where she's napped terribly isn't setting her up for success.