I followed all of Maya's wonderful advice thread on bra fitting and gradually decided I ought to go for a fitting myself.
Wasn't sure where to go but googled and discovered a shop locally run by a former manager of Rigby and Peller (*the* lingerie shop in the UK, which is in London).
Went there this am. Wonderful service and felt amazing all afternoon as I wore my lovely new bra home (was wearing a 36B when I went in, which I guiltily have known for ages should be a 34C. She put me in a 34D, which didn't surprise me at all (- she did put me in a 34C in another make). She fitted by eye, no tape measure).
So thanks for pushing me in that direction, Maya.
Thought you'd be interested to know - she told me she fitted someone at Rigby and Peller once for a custom-made bra. They had to make it from scratch, but worked out from the measurements that she would have been a 42S!!!!