Gas supply

We own a Harmony model from 2002. It use butane 15kg bottles for its gas supply. We have been advised 
that France does not have a supply of such bottles. Is it better to change to Camping Gaz as a source of gas?
I appreciate that a change of adapter is required.

Are there other points to consider? i.e. I presume that the Camping Gaz works on heating and cooking.

Thank you in anticipation of any replies.

6 kg of gas will last for 6 weeks in the summer with 50% of the time on hook up and 50% of the meals not cooked using the van bottle (ie separate BBQ or eat out).

I have to say I'm surprised that you Harmony take a 15kg bottle - I thought 5kg more likely?

I had a Symphony which took a 7kg Butane (or 6kg Propane) and a 4.5 butane (3.9 Propane). I'm sure the gas locker on a Harmony is the same size. If that's what you can fit, I'd go with two full bottles, (have you seen the cost of Camping Gaz, both initially and refills, and you'd need a different regulator.)