Since eBay is an international site, it is important to know what your buying when purchasing from abroad. Below is a basic guide to knowing what size class you fall into. The measurements used are the industry standard. Many shops today use "Vanity sizes" by putting size tags on clothing larger than the size marked, we cannot account for every stores sizing policy but below is the industry standard. Unfortunately eBay guides do not allow HTML tables so this is not as neat as it could be but should be easy enough to use

UK     USA     Europe            Bust                                 Waist                        Hips

8        4           34                  31/32" - 79/81cm               23/24" - 58/61cm       33/34" - 84/86cm

10      6           36                  33/34" - 84/86cm               25/26" - 64/66cm       35/36" - 89/91cm

12      8           38                  35-36" - 89/91cm              27/28" - 69/71cm       37/38" - 94/96cm

14      10         40                  37/38" - 94/96cm               29/30" - 74/76cm       39/40" - 99/101cm

16      12         42                  39/40" - 99/101cm             31/32" - 79/81cm       41/42" - 104/106cm

18      14         44                  41/42" - 104/106cm           33/34" - 84/86cm       43/44" - 109/111cm 

Please remember to rate this guide, and if you are starting in buying or selling check out my other guides.