Be interesting to see who appears on the list… 
British Insurers are the biggest fraudsters I have had the misfortune to meet, if you do not believe me please read take a lok at my website.
I have just discovered that it is not financially advisable to take care of your spectacles here in France.
They are insured for two years by the opticians.
I had to have one new lens and that meant that I could not use my Mutuelle again for two years.
Three and a bit years later I picked up my glasses from my bedside table, put on my glasses and one of the lenses fell out because the frame had broken.
Because my eyesight has not changed, my Mutuelle will not pay, the insurance from the opticians has lapsed and I am left with a bill of over 400 euros.
The manufacturer of the frames does not have any other frames that would take my lenses, so hence the need fot a totally new pair of glasses.
I feel for you.
A boat is a living thing and you invest a great deal of love and care into to it and for you to have been treated so casually is a disgrace.
In the UK I’d just claim on the household insurance as they have broken - is this possible with your French insurer?