We wait till after dinner to open whats under the tree, Mum leave stuff from her in the room, wrapped, we open that when we go in in the morning. Then after dinner we open what's under the tree from family and friends.
Know what I love the most, though, is when you wake up first thing in the morning, and you can smell the christmas dinner through the house, because Mum was up at 4am putting the turkey in the oven so it'd be ready for 1pm (Christmas Dinner Time!) I look forward to my christmas dinner all year.