Ooooh I feel your pain, I really do. I have no actual advice for stopping the early waking but a sort of compromise has been reached after the five am wake ups got a bit much for me. I picked the time of 6.30, before which barring illness or some other catastrophe she does not leave the cot. Full stop, end of story, no, sleepy time etc, even if it's 6.15 it gets treated as a night waking. If she cries I'll go in and check if she's cold or wedged in a corner and sort her out but I don't get her up. When I go in for morning I make a big deal out of it being morning, fling curtains wide, good morning etc, radio on in big bedroom etc, etc and the fun starts and we have a cuddle and feed etc in the big bed then, before she gallops off to persecute the dog, her toys, examine the contents of my sock drawer etc.
The first few mornings she was not impressed but did take the hint fairly quickly bless her. Now I might get the first chatter any time from 5.30 onwards but often now not until gone 6.30 and frequently she realises there is no fun to be had and after a while falls asleep again sometimes until after seven (heaven). I have found that I have to stick to my guns, no taking her off to Mummy's bed for a lovely doze, no getting her up because it's only ten minutes before the time etc as pretty much any deviation from the plan seems to result in earlier cross waking in the days after as she wonders why that morning is different and where exactly is her cuddle, play, feed, song etc!
So not exactly stopping the waking but managing it if that makes sense. Now I just need to stop me waking up anyway!