I start looking out for present bargains around September/October to kick things off. I'm usually finished buying gifts by the end of November.
I buy cards in the January sales. Write them out towards the end of November and send them second class the first week of December.
My parents cover Christmas dinner, though I'll sit down with my dad and plan it all in mid November so that we can get our order forms in nice and quickly. This means we get a much earlier collection time come Christmas Eve, and can avoid the bedlam shops for the rest of the day! We put our turkey/nibbles order in this weekend.
We stockpile various food and drink throughout November/December to spread the costs. Any fresh bits (veg, nibbles, short shelf life, etc.) are bought the day before Christmas Eve, and the turkey collected early on Christmas Eve day.
Tree goes up on 1st December if it falls on a Friday/Saturday/Sunday. If not, it goes up on whatever weekend falls closest to the 1st.
I wrap presents as I go. I'd be sobbing into a bottle of Baileys trying to tackle it all in one sitting! 
DD's stocking is filled on Christmas Eve as soon as she's asleep 