Gas for hob

"natural gas" is running out anyway?with it being used for other than what the government at the time "promised?"

LPG is a by product from the oil industry so will go on for a long time yet 

Not really. There are still those that will use LPG such as plumbers, roofers, fork lift operators and many others that I can think of.

Why not keep simple and use your Cadac for the possible emergency?

I am sure there are good reasons why caravans and motorhomes use gas boilers and not diesel. I am just guessing but I would expect diesel boilers to be more expensive, larger, heavier, less efficient, polluting and not maintenance free. That was basically what I was asking in my earlier post and it would be interesting to know. After all, it would be a lot simpler in theory to take a feed from the motorhome diesel tank - no gas cylinders or tanks.

I think Eberspacher/Webasto is the heating system of choice in self-build PVCs

Why not use a hydrogen powered generator and dispense with gas entirely?

Hydrogen Powered Generator Examples

I’m not sure whether this has been mentioned elsewhere but as we are considering buying a Wildax van conversion we went to the show this week to look at the new models and they have done away with the underslung LPG tank and replaced it with a small locker for a 6 kg gas cylinder. They have clearly thought this through carefully because the heating system is now dual electric/diesel and the fridge is a (very large) Thetford compressor fridge run from the 12 volt leisure battery topped up by a 160 Watt solar panel for off-grid use.I got in touch with Wildax and they gave me the power consumption figures for the fridge which are remarkably low. The 6kg gas bottle should be fine for several weeks cooking only. 
Wildax clearly feel that future pumped LPG supplies could be diminishing so maybe other PVC manufacturers will be thinking of going the same way?