Slightly nervous first poster. I've just had to buy new bras from the Angel range for teenagers in M&S because they were the only ones in my size. I'm 21 
A few years ago I was measured in M&S as a 32DD. At the time I would have been about 15 and was doing about 20 hours of sports training a week on a sports squad, lots of weights sessions etc. I when I gave that up aged 18 I found my bras all ended up being too big so I assumed I just needed to drop down a cup size and started buying 32Ds.
I've now found from lurking on here that M&S fittings are shit, which would explain why I've never really felt a 32D fitted me properly. I know, I know. I went into M&S earlier and tried on a whole load of different sizes myself and came to the conclusion that I should be a 30E, tried on a 30DD and the band fitting was SO much better but the cups were too small. Which makes sense, as from what I've read most people seem to be fitted by M&S as a band size bigger and a cup size smaller. Brilliant, I thought. Sorted.
Except the only bras they had in a 30E were in the section aimed at teenagers buying their first bras. All the other 30 bands in the shop I could find only went up to a D cup. It's like they're assuming if you're a 30E you'll still be growing and end up with a bigger band size. Which I definitely am not. No sports bras in there smaller than a 32 band either.
So the question is, where can I buy bras in a 30E that aren't too expensive?