Hi
Just wanted to let you know that I'm also going through the 1-0 with my DD and we have been in a very similar situation to you!! 5 am wake ups sometimes 4:40 ones!! It's an absolute killer and has been so incredibly hard. I felt lucky if we got a 5:20 am one. Bedtime has been set at 6:30 for the last 6 weeks or more and since then we have been getting these early wakes. I know she is OT but nothing else had been working. I've also held off changing her bedtime due to the clocks changing - so pleased that has happened now!! Of course she had a really short night on Saturday so my dream of seeing 6 am on the clock didn't happen, 5:40 instead (but would of been 4:40 old time). Anyway this morning she actually did sleep til 6:15 (new time) heaven!! (feels crazy to say that)!
I've tried so many different things to change it and OT has certainly been an issue making daytime hard too. I'm now at the point where I'm really happy if she pulls an 11hr night and she seems to cope well on this. I've noticed that after 10.5 hr nights she copes reasonably well, but too many in a row can lead to difficult days. My DD needs a long A time before BT otherwise she just cannot fall asleep, so recently I've found that on days when she has very short night, an early cat nap (15 mins) in the car at about 9 or even early seems to set her straight for the day and she can still fall asleep at bedtime.
I'm longing for her nights to lengthen too!! We've had such a difficult time since Christmas - these transitions - ugh!! Anyway just so you know that you are not alone and if you had text me we'd have been commiserating together!! I've just now set BT at 7:30 as I can't cope with such early starts any longer! Going to just offer a early cat nap when I think she needs it, judging by her night length and mood in the morning and take it one day at a time. Hope you got your pre 6 am WU this morning too! x