I’m a bit late on that one but Alison is right in stating that most house insurances can be ‘extended’ to cover their guests (in that case that’s mostly the guests themselves which are covered BUT also the damage they could cause to the establishment like you would be covered for the accidental damage you might do to your own house).
Barbara is correct as well in assuming that only French written policy will apply, that’s something I’m being asked a lot but unfortunately most companies stopped printing out english written policies as there were a jurisprudence stating that it’s not a valid insurance in France… so everything as to be done in French even though you can get an english speaking broker or agent to get you through the details.
To sum-up, if you are in the gite business you only need a house insurance + public liability stating that you are having that activity (that option should pin point how many rooms are used for that activity) => Guest’s public liability + damages to the house will then be covered properly. Careful though, some house insurances will only include the guest’s public liability not the ‘dommages aux biens’ and in that case damages to the house or furnitures made by the guests won’t be covered.
Hope this is helpful, best,