Thank you for your replies. Since she was tiny she has been a good night sleeper (12 hours-ish) and a bad day sleeper (45 min naps until 9 months old, then 1 long 1 short, then couldn't fit 2 in without APOPing in the car so have moved to one nap since just after 12 months).
My instinct tells me that its molars, I'm just very conscious that i could be 'making excuses' so to speak - i guess i hadn't anticipated that it could/would last this long - i thought it was a few days at a time rather than consistently every night. I have medicated with ibruprofen tonight and will probably dose with calpol 2 at the 2 hr mark just to make sure i can tick discomfort off the list if she wakes late evening.
We will do EBT when she has had a bad night and only one nap (today for example, she got up at 6 having woken up at 8.30, 9.30, 10.30, 11.50, 12.20, 02.20 & 04.10 last night and had one nap of 1hr 45 mins just after 12 and went to bed at 6 and has gone straight to sleep) I try and aim for a12 hour day if its been a bad night with one nap.
With regards to resettling, if she has fully woken and is crying and sitting up asking to be cuddled I will pick her up for a minute or two to calm her, then lay her back down with her dummy & teddy. A resettle like that is only needed maybe once or twice a week. The rest of the time the dummy will do it - we don't interact with her at night & she has never slept in our bed so I don't think its AP in respect to that. Often she doesn't even seem to be awake properly, which i guess would explain why she can't 'think' to find her own dummy.
Having chatted with a friend this evening the only other thing i can think that changed at about the same time (except the one nap transition) is the full move over to cows milk. She has had cows milk in food since 6 months and hasn't shown any signs of a problem with it, but the full move (and so bed time bottle as cows milk) happened at roughly the same time. Is formula more filling and is she hungry? We do baby signing and so she is very able to tell us if she is thirsty or hungry but never 'says' she is during the night if she does wake up, and when we get up in the morning we wait until 7am to have breakfast and she seems fine with that.
Maybe it is the molars and we just have to ride this out for a while longer whilst maintaining trying to not get into any AP habits?