The Ashby Sofa Bed from Bensons for Beds is a nicely specified sofa bed with a price that assumes your guests stay every weekend. Most spare beds get slept in a few nights a year, by people who'd be just as happy on a cheaper one with a good topper. Only pay this much if it'll be used as a bed often.
The parts that are good
It's a two-seater with pocket-sprung seat cushions, so it's a proper sofa first, and that's worth more than people think: you'll sit on it far more often than anyone sleeps on it. The bed rolls out without taking the seat or back cushions off, and that's the detail I'd most want. On cheaper models, making up the bed starts with a pile of cushions on the living-room floor and a guest pretending not to watch.
Inside you choose a foam mattress or a pocket-sprung one, both medium. Take the pocket-sprung one. A sofa-bed mattress is thin because it has to fold away, and at that depth springs hold an adult up better than a slab of foam. The frame comes in two woven fabrics, Ash and Dusk, or a midnight velvet, and it's delivered fully assembled.
The sums I'd do instead
Every sofa bed has the same weak spot: a thin mattress that folds. What makes a guest comfortable is the surface they lie on, and a decent topper fixes that on almost any sofa bed. So the money you'd save on a cheaper frame goes much further on a wool or latex topper, rolled up in the cupboard until someone visits.
Two checks if you're still tempted. The roll-out mechanism is the part that wears on a sofa bed, so read what the guarantee covers. And look at the bed size on the listing before you buy, because Bensons has described it as both a small double and a double.
Who should look elsewhere
Avoid it if it's for occasional guests, if two adults need a full double, or if your hallway is tight: it arrives fully assembled, so measure the door, the stairs and the turn at the top before you order.
What to buy instead
Buy a cheaper two-seater sofa bed with a roll-out mechanism and a sprung mattress, and add a wool or latex topper for guests. If someone will sleep on it every night, buy them a proper bed.