I've had problems keeping my place warm. I'm in a much warmer area than you, but I have more space to heat (~30x25 meters).
This worked well, but the switch failed after two seasons: http://www.amazon.com/Vornado-Technology-Adjustable-Thermostat-Antifreeze/dp/B00FMWPWFY/ref=sr_1_7?s=hi&ie=UTF8&qid=1431099887&sr=1-7&keywords=vortex+heater
I used this last year, and it worked equally well, but it feels more substantial (it's heavier): http://www.amazon.com/Vornado-TVH600-Automatic-Climate-Control/dp/B001EDVU6K/ref=sr_1_3?s=hi&ie=UTF8&qid=1431099887&sr=1-3&keywords=vortex+heater
This might be worth trying:
https://www.youtube.com/watch?v=nzKbFzUEWkA http://www.instructables.com/id/Flower-Pots-Tea-Lights-Heater/
Good luck, sir.