Standard widths for double beds are universal, but, in England, even if you're told you will be getting a double at a hotel, ask about the dimensions in case, by sheer stroke of luck, you discover they mean something bigger. A double bed does not necessarily mean it's big or comfortable enough for two people, given that the dimensions are 4 feet 6 inches in width and between 6 feet 3 inches to 6 feet 6 inches in length.
If you're used to a large bed at home, you might find a single bed difficult to deal with, particularly if you have bedding that doesn't tuck in to keep you pinned to the mattress. Single beds are 3-feet wide and don't allow much space for turning over or for running marathons in your sleep. They're fine for young children, as long as they are tucked in, but adults need a wider bed.
The sizes available in England go from double to king size and then to super king. King size is far more suitable for couples, being 5-feet wide, and a super king is a more generous 6-feet wide. Both are between 6 feet 3 inches to 6 feet 6 inches long, giving you an extra 6 inches in length for the taller sleeper. American bed sizes give more choice, especially with the queen sizes, and the king size in England is 6 feet 4 inches wide by 6 feet 10 inches.
The Sleep Council runs an ongoing campaign in the UK for building companies to build bigger bedrooms in new homes. Bedroom sizes are traditionally so small that the only bed that will fit in with the rest of the bedroom furniture is a double, which gives couples little rest. As of 2011, building specifications have hardly changed at all, and a recommendation that main bedrooms be at least 70 square feet still seems like asking for the moon from builders with their eyes on the profit margin.