Well, I would call it "hems", which of course is totally meaningless in English[:)] Entresol is a low storey between first and ground floor - so it could be that is the correct word in British English. And I think a mezzanine is pretty much the same thing. It seems garret is an unpleasant loft room.

Could we have a native speaker enlighten us, please, we seem to be using French and Italian here...

ok