After considering the options, including a double bed, sofa bed or new futon, we've decided that the best solution for us is an ottoman sofa bed with an innerspring mattress. That way, the sofa won't take up much room, but it can be converted into a comfortable double bed when needed. We're currently narrowing down fabric options from the Wortley and Warwick ranges, and are leaning towards a dark charcoal or grey. Originally I was planning on stripes or something with a little bit of visual interest, but the samples we have look to 'busy' against the carpet. I'll have to add interest with cushions instead!
The next step will be to remove the tiered desk in the corner for something a little more understated (like a simple white desk) so John has more room for his drafting table (which is currently squished in to the right of the desk).
Has anyone out there got a sofabed ottoman (or slept on one)? I'd love to hear your opinion of them.