The main thing is NOT to give up. No matter how much he cries or does other stuff to wake you up, don't show you're up! Keep strong and keep the door closed.

Casper and Kitty had a habit of waking us early too, but we didn't accept that, and didn't give them food. Now they know they're not getting it, until it suits US, and they are fine with it now. Was hard at first though, but it has paid off, nice to sleep longer now and even Casper and Kitty are sleeping longer now