Thanks Yorkie and Bri.
I spoke to my insurer Aviva and they say the home insurance does not extend to other property even on a temp. basis, unlike say car insurance. However the policy booklet does suggest some cover under public liability.
I then looked at internet sites some of which do have information about the issue and it does seem to be a bit of a problem area due mainly to French insurances not having the comprehensive cover that ours and other countries' policies have for landlord policies. I returned to the French property owner with my problem and he has said OK he will just rely on the damage deposit to cover any possible damage.
Other information I found suggested that a good comprehensive travel ins. policy might provide liability cover for this type of situation, but of course I think as Yorkie has pointed out here or elsewhere, for us older less healthy souls, travel ins. can become rather expensive.