Well I did look up Theas measurements she has a 40" bust 26" waist and 38" hip size. Yeah I get to view Theas and Cocos bottams everyday and as nice as they are variety is the spice of life😁
As Thea has said I've no idea about cup sizes. I take it small knickers would fit, although she has got a bit of a bubble butt going on. If it would help I could send Jane a picture of Thea in her Birthda...
Hmmm, for comparison Athena is 33-22.5-39 (a proper pair shape :() so S(8) sized knickers would probably be ok
Black bunny is 35-25.5-36 and sometimes fits better into M sized clothes.
The mesh lingerie is very stretchy, perhaps try that ;)