This is so-o interesting.
I do urge you not to 'correct' your student, coccinelle It is stiil used, and preserves some important distinctions.
If your back kitchen (scullery?) became the kitchen, the kitchen became the living-room and the sitting room ended up being a study, was this not because of alterations in their design and decor for the purpose of changing their use according to changing customs, rather than just terminology?
And for you too, Diane1954, but with the old 'sitting room' staying close to its original function as a 'front room' instead? Don't you suspect coccinelle's study does so too, when her living-room is in the bigger mess? I know mine did before I had a drawing room. But I would never dare to call it that. It wasn't grand enough in the first place, and it's always in a bigger mess than the dining room. It's not at the front either, and we haven't got a 'living room' (unless the kitchen), so guess what we call it?
At least neither of you have one of these dread 'lounges'.
And Lil, what evidence could you possibly adduce for the claim that 'sitting room' is falling out of use?
Yes, Clanad. Here it's 'parlour' of course. There often used to be a 'front parlour' (Diane's 'front room') and a 'back parlour', but I don't see what's circumlocutory about any of these terms.
I admit that the evidence Lil needs might well be your local paper, Diane. Do any of these houses have 'lounges' as well as sitting rooms, perhaps? Estate agents don't eschew 'lounge' without good reason!