LPG costs peanuts though, I don't think theres any tax on it. You can run a V8 on it pretty cheaply, but the tank will pretty much full up the boot.
I had a 100L tank in the spare wheel well. Could fill it to about 72L, which meant a range of around 200 miles. You loose some mpg when running on LPG compared to Petrol (13mpg vs 17mpg on my V8 Range Rovers). The difference in cost is almost 1/2 price, when compared to diesel, usually around here anyway. What I found was that running a V8 Range Rover on LPG meant the fuel costs were probably similar to that of a Diesel Range Rover. Which in itself isn't exactly a cheap thing to run. So you can run a V8 Range Rover relatively cheaply, for what it is, V8 power for diesel fuel costs, but it is hardly cheap.
The cheaper way to fuel a Range Rover would have been to run an older diesel with a veg oil mix, being that you can pick up 20L of veg oil for around £16 or so, and still get circa 25 mpg. You CAN run straight VGO in the summer months, but probably better to run a blend with diesel in the winter months, unless you invest in heated fuel lines etc... But then who wants an old P38 or older Range Rover nowadays (apart from me).
Can't believe no one suggested the Fiat Panda 4x4
Diddums did suggest the newer 500 4x4.