When I moved out of my parents' house, my room was about 50cm longer than a double bed, and about 10cm wider. Still, I needed a bed and wasn't going to be very successful with the laydeez if I had a single bed, so I went and bought a nice, cheap futon matress and base. The company even came to my place and set it up.
I like futons, but the main criteria at that point was price. Futons with a rudimentary wooden slat base were really cheap.
Having returned from our sojourn in London for six years, our spare room has taken over my (much newer than the above) futon sofa bed base. We're trying to find a futon matress for it, but they've really jumped up in price! Cheapest we've found is $319. Ouch!