With the winter coming on this is an interesting thread.
I hope Roy Harding has a read of this thread; I was talking to him a couple of weeks back, he was telling my about a water heater you can get for your static holding tank, runs of the mains.
Heat the water overnight, gues you'd need a well lagged tank! And transfer to your vehicle tank, again, well lagged, gives you hot water to clean your windows with.
The heater is a stainless steel imersion heater, not cheap to buy, but perhaps a cheaper way of heating a tank full of water??
Particularly if you have economy 7.
Something to think about eh?
Keeping your water unfrozen in the winter isn't too much of a problem, you can get the greenhouse style frost protectors to go in a van, either mains or parafin type, or so I believe.
If the winter really is going to be as cold as we are being told, you will have to ensure that your R/O and the rest of your purification stuff are well lagged and insulated.
But that isn't exactly rocket science is it?
Regards,
Ian