Keeping Warm or Cool.
We've found that the portable propane heaters sold in the US (Big Buddy is one) are a great way to keep warm without having to worry about running down your battery - plus you can position the heater where you want it, instead of heating unused space (not a problem when you are in a camper).
To keep cool, we've just purchased a battery-operated fan - haven't had a chance to try it out yet; however, an electric fan placed in an open window on the shady side of the RV and plugged into an inverter works well too. But it does run the battery down, so we're hoping the battery-op. fan works well.