Oh my goodness, I seem to have found not one, but 2 bras that fit! Went on a mammoth bra shopping trip on Saturday, eventually ending up in bravissimo (as nowhere else sold anything that fitted). Tried on everything they had in stock in 28D and 28DD, most of which looked awful - really baggy and wrinkly with additional digging in at the top of the cup - lovely! Then found the bravissimo satine and the bravissimo mademoiselle in 28DD and goodness me, they fit! So I obviously had to buy them and I now have 2 proper bras!
I think in an ideal world, the cups would be a tad smaller while still having the same width and depth of wires, but without being tighter on the top, but I don't think that would be possible without having a bra tailored for me.
The question is then, given that the satine and mademoiselle fit, what else could I try that would give a similar fit? I tried on a few freya bras in 28D and DD in john lewis (lots available in the clearence just now) but I was finding the lace at the top of the cups either wrinkled or dug in.
Thank-you for all your help! I was so happy (and rather amazed) when I found the right bras!