It might be better to get a small plug in heater until you get the main one checked out. I wouldn't use a fan heater or anything with radiant bars while you're not there, but a panel heater or small oil filled radiator would be ok. You can get circuit breaker adapters to make sure they are safe when left on. I just started a new thread on keeping hammies warm which might help
Keeping hamsters warm in winter
If all else fails, turn the oven on
That's what we did when heating broke. But only when you're there obviously! Electric panel heaters or convector heaters are more expensive to run, on the electric bill though. The oil filled radiators are quite cheap to run.