Lay out your running kit ready for the morning and have an early night (get some winter running gear for when it's cold). Plan for a slap up breakfast when you get back (of course, if you bottle out of the run, you're not allowed the nice breakie).
When the alarm goes off, get up straight away and get the kit on. Don't give yourself time to think about staying in bed.
It's not a feasible option for many, but what about getting a dog? My labrador hears me the moment I'm up and won't let me be until I take him out.
Lozf - cold & crisp, yes, but there ain't much sun at 4:30am in December!