I stayed there with two of my kids for a week. The place is not too large, but nicely equipped with everything needed. The apartment is nice, but the building is not the newest.
The beach is just a short walk away. It's half an hour walk to the center of Concarneau, which is doable. There isn't much infrastructure very close, but enough to get bread for breakfast, and also a bar and some restaurants.
Communcation with the host was pleasant and easy. Overall, it was a pleasant stay.