Bravissimo does anything above a D cup - but no, an F on a 30 back isn't massive at all. Roughly, a 30F, 32E, 34DD, 36D, 38C etc etc all have the same volume. It's just that most people wear too big a back size, so they wear too small a cup.
That and the press claiming ridiculous sizes like the article the other day that said Kelly Brook was a 34E - ha ha ha ha !
Well I got a 30FF, ordered a 32FF which will hopefully turn up in a few days, because they didn't have the colour I liked in stock and I have bit of paper with the details of a 30F sports bra I liked but didn't have the cash for.