Just take a full bottle - 6 kg of what you normally use. In summer it will easily do 6 weeks - if winter or going longer, take 2 or buy a euro bottle there and adapter if necessary.
Do you mean you use bottles, ie Calor or do you have a fixed refillable lpg tank underfloor? If you have fixed tank that you refill with autogas at service stations then any lpg vehicle specialist will have adaptors for autogas pumps in other European countries.
If gas bottles, then as stated, a 6kg Calor bottle will probably do you cooking only for 8wks or more, but start running fridge, onsite contiuously then probably 2.5kg/per wk incl cooking, use gas heater & even more so 6kg bottle might last you less than 3wks.
Post up what setup you have & then further assistance can be forthcoming.
Does your fridge not work on electric? And get yourself a two ring electric hot plate and use the electric you have already paid for, we do it all the time, very rarely use gas abroad
Don't forget to leave a review of the French and other European campsites you have visited!
Yes Shirley you do need adaptors for refilling your LPG, there are three of them that cover Europe - we paid extra for ours when we got the LPG system.
We have found most garages in Europe have a box of adapters so rarely use ours, but would recommend you get the ones for the countries you intend to visit.
Also worth checking in advance for LPG stations in the countries you intend to visit - it does vary greatly - LPG stations in Europe shows all that garages that sell LPG, not every garage sells it and it some countries we have found the website a real bonus where only a few retailers have LPG.
------------- Never argue with an idiot, they will bring you down to their level then beat you on experience.
Land Rover Freelander 2 & 2014 Lunar Quasar 554