Joff, I think under your Motor Registry code, any vehicle that has been subjected to fire of level ......, is never able to be registered again and is classed as a statutory write of, only good for parts to go on a repairable write off of road worthy car.
However if it hasn't been through the insurance/motor registry process, there would be little difference to it being a rusted out repairable Moke. It will all depend on how badly burnt(rusted) it is.
Photos would help.
Cheers
Dev