Now, with a great deal of help from julia_winolj, I've been generally sorting it out. As of a couple of weeks ago the room's been more-or-less empty of all but a few large items of furniture.
And in anticipation of the imminent arrival of guff_peeps on Monday, it's now very nearly ready for habitation -- it's been hoovered (although new bits of dust keep emerging from somewhere), I've got clean bedding on the bed, and I've just installed a curtain-rail and hung new curtains.
Of course with the combination of the colour of the bedding, the colour of the carpet, the colours of the walls and the colour of the curtains, I'm practically bound to have got them all completely mismatched.
Still, I've now got a whole extra room in my house! Hurrah!