I too doubt whether holiday cottages would fall under the FSO, as for instance, a group of students sharing a house for a few terms wouldn't, so why should a family of four (and a dog) attract such attention???
Correct me if I am wrong, but I would have thought that the students example would constitute a HMO in the proper definition of it, (unrelated persons, shared facilities, truly a "
House in Multiple Occupation") and as such would be enforced by the local authority. (FRS would technically have the common areas, but where I am it is policy the let environmental health deal with the whole building unless we are aware of dangerous conditions.)
The difference with the holiday let is that the people there would be generally one family so would not constitute a HMO by definition. It is more like someone mentioned earlier, like any family renting a place to live, albeit for a short time.