I would be careful because heater blankets are not meant to be left on all the time. Your best option is a ceramic heat emitter (CHE) with a thermostat to control the temp. You set the thermometer to the heat you want, and anytime it goes lower the ceramic heat emitter (CHE) turns onto keep a steady temp for the hedgie. They can be costly when you initially purchase them but they pay for themselves easily and the bulbs can last up to 5 years.
You can get a CHE from any pet store, as they are primarily used for reptiles. The CHE heats the entire cage, not just the bottom like the heated blanket would, but not the whole room which is nice.