You could also look at raising the ambient temps in the room the snake is in either with your own home's heating system or with a supplimentary heating source like a good safe space heater. We have some in the states that are oil filled with the oil being heated electrically. If you choose this option make sure you do buy one with the tip over shutoff function for safety reasons and a good on/off thermostat on it so it doesn't continue run once it reaches the temps you want. We have one in our snake room and it works very well in the cooler months to keep the room at a steady temp (an old Acu-Rite is on the wall so we can watch the room temps and humidity and adjust accordingly).

Here's a link to Lakewood who supplies these types of space heaters. Also a picture of a similar one that is retailed by Home Depot (just to give you some idea of what I'm going on about LOL). Locally I can find these for around $40-$50

http://www.lakewoodeng.com/html/list_oilfilled.html