Webasto
 

I think you would have to do your research on webastos - quite a few different types - some warm the engine and the cab with a timer, some even have a remote control.
They are the best way to keep warm though.

Hi Darrin,

Just to let you know that we bought this fan, £55. The make was a Hella. Looks great, but need to get some serious heat to know how well it works.

Thanks for the tip and hope you had a good Billing.

Bought one ceramic heater (fan and heat) on eBay, cost me 25bux and works great, can't find the references anymore but you should find it easy on eBay of you search for "ceramic heater"

On the subject of catalytic heaters; I bought a Coleman "black cat" burns gas, when they were half price (£29.99, Oswald Bailey) this heats a small tent in about 10 mins, if you could place it somwhere safe they are excellent. Drawback is you would have to take enough gas from UK because I'm not sure if you can buy it elsewhere.
Only to be used when awake with adequate ventilation.
K