Heating of Vivarium in a cold room

Im looking for a little advice here (again!).
I currently have my corn in a large geoflat with a heatmat on a simple on/off thermostat. This is fine at the moment as the ambient temperatures are pretty warm. However, in the winter my flat gets very cold. Without heating it can drop to freezing.

I am looking to buy a 36 x 18 x 18 viv to move her into for this winter and beyond. Ive been looking into it and have decided that my best bet for keeping the temperatures stable and high (I dont intend to brumate her as its her first winter) is the following.


1) Have a melamine viv (flatpack jobby) and install a 150 watt FTE ceramic heater + guard in one end for the hotspot and main heatsource attached to a dimmer stat. This should give me more than enough heat to combat any lows in the ambient temperature in the room.

2)Optionally, have a heatmat on a seperate stat at the 'cool' end of the viv to maintain the 21 degrees temp required at that end.

Id rather have heatsources attached to the tank that can maintain the required temps without help from my central heating as its gas powered and very expensive. We generally only have it on a few hours a day.

Apart from the expense of the electric bills can anyone see any possible problems with this setup? I am prepared for this to create a very dry atmosphere which I will need to combat with a large shallow water bowl or light misting daily, is there anything else anyone can think of?