not sure if weather is the same there but in maine we have below 30 temps most of jan/feb and alot of december some of november, we use r-19 insulation in walls and r-30 or higher in ceilings
i would want a 50-70k btu heater
http://www.heatershop.com/propane_garage_heaters.html
http://www.heatershop.com/mrheater_p...r_mhu45lp.html
2lbs of propane per hr of run time, in a properly insulated garage it should only run 10-15 mins per hr
model- mhu-45lp would be a good source, you could use your own propane tank also, lowes and home depot sell 100 lb tanks which hold 24 gallons cost about 70 bucks to fill and would last a week or so of constant heat if properly insulated
http://www2.northerntool.com/heaters...tem-173637.htm
lastly modine is a good commercial name model 45 also
http://www.littlegreenhouse.com/accessory/heaters.shtml