So I've done the measuring (31" underbust, 37" bust) and have gone trying.
Been to John Lewis and tried their own balcony bra, two different Elle Macpherson balcony bras and a Curvy Kate. The band at both 30 and 32 feels good, I am probably ok with 30. But the cups, oh dear. They are just too big! I've tried 30e and 32dd - where have I gone wrong and where do I go from here?
I definitely need a balcony style because my breasts at the top are pretty flat (things they don't tell you about pregnancy and breastfeeding) but I need to do this online from now on as the sizes available were pretty poor in store.