We have the same issue here, DS wakes anytime between 4am and 5am and is ready to start the day irrespective of what time he goes to bed. We recently bought a gro clock and have set it for the sun to wake up at 5am (while not great is a sleep in for us) So he knows that when the stars are on the clock he has to stay in his cot and in his room. We normally go in and give him some books to read or toys to play with but have emphasised that mummy and daddy will not play until the sun is awake. We are slowly moving the wake up time later and later each day and while the process is not easy, it seems to be working better than anything else we have tried.