In reply to ImperialJohn:
As others have said, you don't want a wood burner in your tent unless it has a chimney. (so not an ultralight option!)
I have used Tea light candles in the porch of a backpacking tent in the winter and one of them will make a surprising amount of difference. You do need to be very careful though and not be tempted to use it in the tent itself. I always leave the fly zip open a bit to allow airflow.
I used to fill a Sigg water bottle with hot water last thing, put the bottle inside a sock (a great way to dry out damp socks you will need the next day) and use it as a hot water bottle. The water will be cool in the morning but will still give you a head start making that vital first brew.
On the whole a lightweight gas stove or a jetboil might be a better, more versatile option but whatever you decide is your call so have fun and take care.