Well done!
Keep your water bottle in a sock in your sleeping bag. Double-check the lid. The sock with absorb any leakage if you miss it, and keep the water from burning you, or chilling you if it cools. I prefer to use boiled and then slightly cooled water (depends on what your bottle is made of, so try it at home first so you don't melt it) - I tuck it near my core when I climb in, and I am nicely warmed. Large water containers should be turned upside down and buried until needed. There is lots of great advice in the Winter Camping sections of this forum
:)