Switching to propane

I would also fit a new flexible pipe when changing to a  propane regulator ,good luck with obtaining a propane cylinder

Yes, you are correct, you need a propane regulator to screw into the bottle (note it's a left hand thread). I echo the above comment about changing the 'pigtail' pipe between the regulator and the van's metal pipework unless it was replaced in the last 4 years. 

Ebay/Gumtree etc are the only places you will get a 'new' propane bottle, they were like gold dust in the summer and often priced accordingly!  If you're going for Calor a new bottle charge would be £40 so if you can buy an empty for less than that you are quids in.  Be aware that Calor will not exchange bottles for different sizes or swap equivalent propane/butane at the moment, I don't know about Flogas, but I'd recommend calling ahead to check if you were thinking of a "gas swap" with them.

It is recommended that caravan gas pigtails should be changed every three years anyway, 

Thanks All