Автор, знакомый профессор, англичанин, ответил:
"Technically, the Manor House was the home of the lord of the manor and the administrative centre of the manor. However, the term ‘manor’ has also been extended to indicate a large and noble house belonging to families of the small nobility during the late medieval period. Although their house was often fortified, it mostly had the function of displaying the power and importance of the family, rather than defending from intruders.
Manors are the most ancient (mediaeval) of the three names, but of course, they were often completely trasnformed in the 18th or 19th century, or destroyed and a new building erected on the same site but with the same name. Or a brand new house was just called a "manor" to give it some "pedigree". For instance Waddesdon Manor is a huge house built for the Rothschilds, but it was built in 1870!
As for "house" and "hall"—you might think a "hall" is a grander place than a "house" but, for example, Eyam Hall, pretty small place—a big farmhouse really. Just down the road is Chatsworth House—one of the biggest places in Europe, built for the Duke and Duchess of Devonshire.
And Haddon Hall is really more of a castle, isn't it?—another term.
Downton Abbey is actually Highclere Castle...