This link http://www.leparticulier.fr/jcms/p1_1501503/une-facture-d-eau-plafonnee-en-cas-de-fuite does mention the limitation you mention, Annette, but my reading of it is that if the link is in your washing machine, central heating boiler or dishwasher then you have to pay. Doesn't seem to apply to the pipe leading to the machine and therefore not to the pipe leading to your bath. I'd just send them the proof of repair as required and claim the right to pay only twice your average annual bill and see what they say.