XS    S   M   L XL
PTP 15.5" 16" 17" 18" 19"
Waist 12-12.5" 13" 14" 15" 16"
Hip 17.5" 18.5" 19.5" 20.5" 21.5"
Length 32.5" 33" 33.5" 34" 34.5"

*Model (wearing Corn Yellow) is 1.70m, UK 4/6 (PTP15", Waist 11.5", Hips 16.5") wears size XS.
*Model (wearing White) is 1.64m, UK 6 and wears size S.

If you are in between sizes for PTP/waist, it is best recommended to size up. 

*In between sizes refers to your measurements falling between 2 sizes, example size S & M.