Our spare room is approx. 7" by 8" and we got a double bed ( 4'6"x 6'3" plus metal frame ) and a large wardrobe. Ok it was a little difficult to get to the window, but that was partly because my friend ( who was staying for a while ) refused to have the bed anywhere else in the room. I can't emphasize under bed storage as a total plus, enough. A folding bed loses that advantage. You may be able to go with a large single, with drawers underneath as WYSIWYG said.

You can either buy or make quite easily, a table top that bolts to the wall on hinges so you can drop it down when it's not in use. A folding chair for somewhere to sit that's not the bed.

Is the fireplace used, a feature you like or would it be possible to enlarge the opening to make into further storage space.

Little things like hooks on the back of the door and around the room ( e.g. to hang the folding chair from...) can make a big difference. Keeping as much floor space free as possible is also a must ( I know this sounds at odds with trying to cram stuff in )but it makes a huge difference if you're not constantly banging you toes off furniture.

Mainly it depends on exactly what you want put in the room.

I like the idea about scouting out caravan outfitters.

Good luck!

TTFN M'Lady P. ( who only acheived a bedroom bigger than 8'x10' when I finally left home at 27! )