Peugeot Executive 97 2.5d

The refillable bottles cost about £8 to fill (depends on the capacity, the gas costs about 80p/ l) in Europland. The same bottle of Calor gas here is about £40.
You have to decide how often you would refill it and thus how long it takes to get the original cost back. You can of course buy the bottles used, for half the new price. In France it is so plentiful that you can drive round town looking not merely for a filling station, but looking for the cheapest filling station.
Once you have bought a bottle you can of course keep it and transfer it to a new camper. And of course in Europland you won't find Calor gas anywhere.

Phew that's expensive. I thought the whole kit new was about that. Keep looking. You can buy the bottle used, but you will need to get new hoses and the filler nozzle. It's easy to fit, you are allowed to DIY, you don't need a GSR chappie.
As well as GasLow there is GasIt, they are the same thing, same sizes, same filling system and so on. IF you get one with a gauge on the top, they aren't very accurate, and really not worth bothering with. When your hob flame gets low, it's time to look for a filling station.