just a thought.
if you're going to be on electric hook-up most/all of the time, what about buying a small electric hotplate (£20) to use outside for cooking, and maybe a small electric heater for heating inside (depending on the time of year)? would save a considerable amount of gas and you may find that one gas bottle would last the entire time.
we go to france for up to 7 weeks twice a year with our caravan, as well as using it the same amount in this country, and our last gas bottle lasted two and a half years.