Well, I figured this was such a cute bra, I'd try it again. Based on the measurements of the 30G (here on Bratabase), and my experience with how stretchy the band is, I ordered this size. I even ordered the matching panties in UK 10, because I was feeling whimsical. Anyways, it's pretty comfortable, but it feels all-over too big, so I'm going to exchange it for the 28G, which has already been reserved for me, and I'll put that up after it arrives.
This option didn't exist in the review, but there's gaping at the upper corner of the bra-- I wouldn't say it wrinkles, since it's a moulded bra, but there's definitely a weird space there.
I haven't worn a t-shirt bra in a while, so it might just be that talking, but ohmygoodness it is so comfy!!! I really, really wish the straps were more adjustable though. they are definitely verging on incurably too long.