What size is a UK double bed?

A UK double bed measures 4ft 6in (135cm) wide by 6ft 3in (190cm) long. The mattress is the same size. Width per sleeper is 67.5cm, the smallest commonly-sold couple-size in Britain. Small doubles at 4ft (120cm) wide exist but are usually marketed for single sleepers who want extra space.

Will a king-size mattress fit a double bed frame?

No. A UK king is 5ft (150cm) wide and 6ft 6in (200cm) long, so a king mattress is 15cm wider and 10cm longer than a double frame can take. Order the matching frame size: 4ft 6in (135cm) for a double, 5ft (150cm) for a king.

Are storage beds worth it on a double?

Yes if bedroom storage is tight, less so if you already have a usable wardrobe and chest. A double ottoman gives roughly 200 litres of useful capacity; a divan with two drawers gives about 85 litres. The trade-off is mechanism wear: gas struts and runners are moving parts that solid base beds do not have.