Don`t know if you know this guys but if you need to carry a gas supply then the cheapest is the 47kg cylinders. If that`s too bulky then the cheaper method is to fit a lpg tank and fill it at fuel stations. I have a friend with a small camper. the small bottles are equal to £2 per litre of gas where the lpg is less than 80p. The cost of an lpg tank for this purpose is not that much and you will soon re-coup the outlay, or buy 47kgs at a time. That equals 54p per litre.
Just a bit of info you might find useful.