The following are standard mattress sizes in the UK:

Small Single: 2'6'' x 6'3'' or 75 x 190cm

Single: 3'0'' x 6'3'' or 90 x 190 cm

Small Double: 4'0'' x 6'3'' or 120 x 190cm

Double: 4'6'' x 6'3'' or 135 x 190cm

King Size: 5'0'' x 6'6'' or 150 x 200cm

Super King Size: 6'0'' x 6'6'' or 180 x 200cm