Hello Wendy,
sorry I've only just seen your post, I hope I'm not too late
What I did - I did not wake him, I think that would have made him overtired, I just let him sleep, then for the next four days, wake him up 15 mins early. So, (new times) 8 am the 1st day, 7.45am the 2nd day, 7.30am the 3rd day, and so on until lo is waking at normal time. That make sense?
HTH