fair enough gents. thanks for your advice, i will stick with the candle!
And a hot water bottle
Wood burners in tents effectively take up one third of the useable space, you'd only need to roll over in the night to burn a hole in your bag.
There are those baked bean can type heaters that sit on the gas stove, radiate masses of heat. I can't think of the name of them. As with anything powered by a fuel that emits CO, you can't leave it burning in such a small space. To an extent, canvas breathes, and my tent is roomy. When I was using my Oztent with doors and vents closed, I just made a cuppa before bed and that heated the space enough, same in the morning. Once in bag and snuggled, why need heat anyway?
I confess to owning a Gelert tent heater that served fine during an October camp in The Lakes. Bit glamp, but it really worked very well, and I was careful to switch it off and have a small vent open.