it is hard isn't it?
I followed the idea of night time = quiet, dark, feed in dark, no eye contact, no playing, no nappy change unless essential (and even then, how about changing it at previous feed and then it will last?)
If they wouldn't sleep, I took them into my bed and was cuddly, but not 'fun' until morning.
When they were a little older, I used to give them their cuddly toy and say, Shh it isn't morning yet and tuck them back in. Again if they wouldn't, they came in our bed and it was boring.
All mine eventually slept through til 7 regularly, but I have to say, I don't assume it was my method at all!
I think you can play with bedtimes, and feed times, and they still wake early and want to play. Sometimes, you just need to give in and go to bed early.