Mmm- interesting question @ScottishMouse and @Stoic123 - the bodice is quite form fitting on the orange and dark green - at least on me! Assuming the black is the same, you would probably have to size up, but how that would work/balance with the skirt part of the dress, I don’t know.
What I do with the green and orange ones is I either wear a short sleeveless boxy Toast tee over the top or my lacy mini poncho/shawl thingy that has finally found a use or I go bra-less, depending on the heat/where I am going.
Given the size of my chest area nowadays, it’s testimony to the quality/thickness/supportiveness of the bodice that it doesn’t look completely ridiculous without a bra.
I love those dresses so much. If the black one wasn’t still £90, I would get that one too! I think they are my favourite/best Toast purchases apart from a couple of my jumpers and, of course, the Pond 😹