Thanks for all the replies.
So the annexe in question used to be a garage (separate from the main house) and had a kitchen and bathroom put In by the previous owners. They rented it to family
members.
Now we have renovated it and would like to rent it on air bnb, (it’s not large enough to live in!) and I want to
know if I should apply for change of use. I understand from my research that if a family member was to live in it I wouldn’t need to, but I don’t have a need for that currently.
Obviously I don’t really want to have to apply for change of use unless I have to, as it’s expensive and from researching some other case they might even say no. Despite it being good for tourism to do so?