One of these might be useful - A Foker Double Gas Boiling Ring with Flame Failure Device (FFD)

http://www.gasproducts.co.uk/acatalog/Double_Burner_Europa_Gas_Boiling_Ring_with_FFD.html

It can be used with a whole host of external Gas Bottles (Butane Propane or LPG) from the Campingaz 901,904 bottles etc through to industrial propane bottles using the appropriate Regulator/Hose and Clips etc i.e most of the bottles supplied by Calorgas such as the Butane 15kg bottles and smaller Patiogas bottles.

A single 15Kg Calor Gas Butane Bottle would give about 25 hrs continuous use at the full 8KW output. Or to put it another way around 15-20 weeks normal cooking use for 1 to 2 persons.