No idea, best to contact your local planning department for an informal chat. If they did say yes I would certainly want to be able to add windows for extra ventilation and light so check that at the same time.
We did in our last house, although the building was an outbuilding originally used as stables, converted to a garage and we converted back. We didnt get any consents. Ours worked quite well as we were able to keep one of the garage doors permanently open (garage had double doors) so very airy, we had benefit of stable windows from previous use and we only put to stable door height partition walls in so they could socialise (they were generally pretty friendly)
I did it. I just assumed I didn’t need permission TBH. But the guy who did the work for me is pretty clued up equestrian contractor and he said I didn’t need it.
We lived in a 1930's brick semi, with the 1930's single garage and converted the garage into a stable one winter, with false wall and stable door 6ft in.
The last but one house had a cattery that we converted to two stables. There are local bylaws that the council sometimes enforce but most of the time if you are not a nuisance and have a good relationship with your neighbours you are within your rights under permitted development as a horse is a domestic animal. There is a limit to the height of the building.
I did-its a big pitch-roofed workshop/garage building with an inspection pit in. We got that covered, 2 really large stables and a storage area, plus tie up area-no planning but we're in Scotland and in no way overlooked. Our stable company were able to advise us on planning etc.
unless the law has changed recently as far as I am aware you are allowed to build stables within the curailage of the garden without planning permission