I've put that escape plan on hold after three days of contemplating the matter.
For I now have access to both of the top floor rooms and I'm presently reclining on my feline-attuned friend's desk as he receives this dictation. (I would type the whole thing up myself of course but the keyboard is rather poorly set out for paws).
I've also started to meow, in moderation of course: for a single meow should command sufficient attention in its own right. However, I'm still slightly nervous about approaching footsteps and prefer that the visitor confirms his identity before I extend either a swift welcome, or maintain a safe inspection from beneath the spare room bed!
Still, such early days but there's the stairs to explore tomorrow even if the lobby below seems somewhat secure. Besides, I'll not venture down there unless the door of my own good room remains sufficiently open to ensure a rapid retreat from any strange sounds.
And there's another - you'll have to excuse me while I dash off to survey my domain. . .