http://www.spacesavingbeds.co.uk Why have a dedicated guest bedroom for chance visits when you can have a working office that serves two purposes? (By the way, everything on the desk STAYS PUT when the bed goes down)
Floating Desk with Storage -- love this design for something to build one day, for extra work space for guests or moving around the house. Could work as a small craft space, and/or could be combined with fold-down/fold-out elements. This has lots of potential.