Hi, and good afternoon,
Whilst it sounds absolutley idyllic, 'most' carp anglers go to france to bivvy up next to a lake, to fish for a week 24/7 with a chance of catching big fish.
I think you would be better suited to advertise as a holiday rental, with fishing as a local activity, rather than aiming it purely at carp anglers.
Also, look into getting a SIRET number (Not sure if it applies?) - as there are a number of people who post on each and every 'fishing in france' thread requesting / looking this information up, and then bad mouthing the place if its not registered (Yes, I can understand why they do it).