This is Vicki. She models all of our size XL jumpers. She usually wears a UK size 18-20. Her measurements are:

Height: 5'7", Bust: 44", Waist: 42", Hips: 50", Arm Length: 22"

Size UK/US Bust
Extra Small UK 6 / US 2 up to 32"
Small UK 8-10 / US 4-6 34"-36"
Medium UK 12-14 / US 8-10 38"-40"
Large UK 16-18 / US 12-14 42"-44"
Extra Large UK 20+ / US 18+ 44"+