In my 1200x600x500 enclosure I am using a 100w ceramic + a 60w i/r heat globe.
In the 900x600x450 enclosure, I have a 100w ceramic + a 40w i/r heat globe.
We are in Vic and at present the daytime temp is around 12 to 15 degrees, with night time temps getting as low as -3, but usually around 4 degrees.
The reason I have the globes, is so the missus can see the snakes of a night time, she is petrified that they are going to get out

otherwise I would have a higher wattage ceramic.
Cheers, Spyke