UTH's do not change the air temperature in the cage, air temperature is important espicially in a room as cold as yours is. The air temp shouldn't ever be under 75.
I would suggest that you get a Ranco thermostat to regulate your space heater, they can handle the wattage and are commonly used in the reptile industry for this.
You can get one here: (make sure you get the room heater version and not the outlet strip)
Thank you, that's excellent advice. My heater supposedly has an internal thermostat, but I'm not impressed with the way it functions so far, and of course there's no way to set it except to fiddle with the unmarked knob and hope.