Having been given plenty of advise over the last few days, and trawling through old threads, ive decided to get a fresh water tank heater. It will get fitted next wed. Additional lagging of all the pipes and insulating the tank will also be done next week. Ive found some insulation board http://www.insulationexpress.co.uk/...x-Multi-Board---The-Original-Marmox-Board.htm I will line the tank with the board as best I can then suround the lot with double foil insulation roll. The pipe lagging will also be wrapped in the foild bubble where possible for some added insulation. I've also got side skirts for the open areas around the van to minimise cold air movement. Oh and an inside/outside thermometer to monitor the situation. Cheers all for the tips Should keep things moving up in the highlands.