[paul middleton]

I fitted a boiler last year and the only time i use it is on conservatories that don't have heating. And it will find any weaknesses in the hose, also it comes out lukewarm not that great. But it will not freeze.

[FCS]

IMMERSION HEATER ELEMENTALs my dear watsons, it's the way forward I'm telling you!

No freezy for me yet, and no cracky glassy either, cos although it's hot in the tank, by the time it comes out of 100m of hose it's barely tepid, but FINE for windows, and keeping hoses nice and flexible too.. 
No faffing with gas bottles or all the insurance issues that could arise from that, not to mention the space a gas bottle would take up in the van.. No sir!

[G Griffin]

I believe hot water freezes faster than cold water, for some weird quantum reason, so does warm water in your hose not freeze if you're working?

Not always. There are many, many variables to take into account and I don't think a wfp system was a consideration when the Mpemba effect was 'discovered'.
Water will freeze when it reaches freezing point.

[Richard iSparkle]

I often wonder why you shouldn't put hot / warm water on your windscreen in the cold  in case it cracks, but you can clean windows with it, could it crack the glass aswell ??

you can crack glass if the temp of the water is too hi.  i've done this myself when i jacked the temp right up on first cleans for a bit.  if there is a fault in the glass cutting you can cause this to go.  it wont crack a properly cut piece of glass, but of course if the fault is at the seal (where the factory cuts them) you cant see it.  if you keep the temp warm, say 30 deg  you wont have a problem.

[Richard iSparkle]

How fed up do you feel with this weather, personally i find it very annoying when you heat van bring in trolley etc, only to find that you reach your 3rd job and the pole hose freezes water as it pumps, i knew this would happen if i used the hose reel on the ground but thought id be safe enough with trolley, can anyone tell me if this still happens with hot water fed pole systems, or is that the answer and way forward??

the short answer is YES.  we had days last year when we had problems with our hotwash (due to batterey probelms it turned out) when the temp was really cold (minus 8 etc).  when the hotwash was working we could work no problem, when not working we were slowed down, or couldn't work.