I've never been into the place but if it's been playing music at the same volume for 28 years without issue then I'd say the new resident is being unreasonable.larger venues have to comply so why shouldn't small ones? The Royal Albert Hall has to stop performances at 1030pm and that has been there 150 years.
As no details were provided by N&D it is hard to tell who is being unreasonable.
Maybe more to the story so happy to wait and see but on the face of it I'd stick to my original view.