Whilst the Bus is sat on the drive, I use 1 of these, on a low setting 24/7, just to keep the chills off.
Discover more about Nano Oil filled radiator 500W TRNS0505M and buy it on the official De'Longhi website at the best price.
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Used it for the last 5 winters

Open all the drawers/ cupboards etc.
Our camper is kept fully stocked with a mattress / quilt / sleeping bag / pillows / rugs - so this 500w oil filled rad, does the trick.
Never had any issues with frozen taps / bottles / pipes.
Don't know what it costs to run, but it deffo keeps damp at bay