when my dds were younger dh had a genius idea - he attached a night light to a timer (the kind you plug into the wall socket like the ones people use when the go on holiday to switch the lights off and on) and he set the light to switch on 5 mins after the dds were getting up
at this point they were waking 530 each day
he put it forward 5 mins each day til we reached 630am
it worked
they went from getting up at 530 to gettng up at 630
they would come through to our room "mummy mummy i can get up now the lights on"
we were going to aim for 7am but i didnt want to push it