hi bornabirth
i worked in a shop here in uk that sells clothes.I am size 26 or 27 in the phils but i am size small or medium. But here normally i am size 6 regular or 8 short and sometimes size 11 -12 for children:d oh so difficult to find my size here.
regarding underwear it will vary.. i buy small underwears some are big some are ok lol!
hope this will help.
goodluck
ann