Dd measures 29 tight underbust & 35 loose overbust.
Dd was wearing a 28D but it was getting small so she was re-fitted at John Lewis as a 30D. The assistant said she would like her to try a 30DD to compare but they didn't have any in stock.
That was back in January. She has grown a bit (from a dress size 6 to a size 8) Because she wants a flesh colour bra she went herself to M & S & bought herself a 30D but I think it's far too tight. I got her to try in on backwards & the band ok, maybe a bit loose so it's cup size she needs to go up. She says her JL 30D still feels ok. I also got her to try her old 28D backwards & I think the band fits though dd pointed out it has stretched a bit.
I think I'm going to have to order online but am not sure which measurements to start with.