Well the spare rooms haven't seen any use for five months, I don't see a problem with giving one up. Although it might take a little extra time to move the furniture to tidy it up properly, and the acoustics might be terrible.

[ He drums his fingers on either side of the stool he's straddling properly. ]

Would you need that textured foam on the wall? The type they have in studios. I assume it's something to do with acoustics, or is that sound proofing?