I have the same unit as dcheatwood so when the fireplace on low doesn't quite cut it, I break out the Caframo heater (sold here in Canada as the Home Hardware 'Classic').
To use a space heater without concern for exceeding your main breaker rating, you can install one of these: GCP1 | Genius Battery Chargers
and run a heavy duty extension cord to the 15A outlet on the power pole. Looking at dcheatwood's picture, I installed it through the side of the side just about where his shoes are.
2015 Rockwood Signature UltraLite 8282WS Platinum, GY Marathon LRD, TST 507RV TPMS
2005 GMC 2500HD CCSB D/A, Curt E16, Prodigy P2, Garmin RV760LMT w/BC-20 b/u cam