fit an immersion heater in your tank then on cold days leave it on timer at night it will keep your water hot all day cost 70 pence a night far cheaper than LPG etc cost to have this done by a good plumber £140 ish and will stop your poles and battery and pump from freezing
I'm with this guy, I have an immersion fitted for winter, leave it plugged in overnight the tank acts like a radiator keeping everything frost free, and the hose will still melt thru snow after 8 hours of working. All fitted for about £60 in materials and 1 hours work tops.