The cheapest I've found this one is £25. The single is £14.99 plus postage on amazon.
Great for camping, or family/friends staying around over xmas/new year - which is our reason for the purchase.
A double flocked finish airbed with inflatable pillows that lock into place. Unique Snap'N Stay closure system. Storage under each pillow. Durable PVC which is highly puncture resistant. Repair Kit and Carry bag included. Airtight system: patented double lock valve locks in air two ways.