You could just get fixed broadband for the holiday home and use that? Then add WiFi as a selling point for the holiday home.
Yes! B is spot on. I rent holiday cottages several times a year and wifi has made it onto my "must have" list. Until recently it was not commonly available but there is now a situation where I can afford to ignore cottages without, in the knowledge that there'll be another not far away that has wifi.
So put it in and mention it in your cottage features.It is enormously helpful on holiday for looking up the opening times of local attractions and the like. Don't forget that phone data reception is often **** in holiday home locations. Go for it. It really is a selling point.