I am 6 + 3 and my knockers are in need of some new scaffolding. I am just about fitting into my existing bras (not the padded ones, they haven't fitted since I POAS).
I consider myself to be reasonably bright and I sew a lot, so I am handy with a tape measure. But I am totally 
about the measurements.
It doesn't help that Marks and Spencer and John Lewis seem to have two completely different systems. I usually wear M & S bras and have generally found them to be comfortable. I don't want to go to the John Lewis near here tomorrow, which is small and has mostly expensive stuff in it, to spend a fortune on a bra I will grow out of again in two weeks.
Does anyone have a definitive answer on how to measure and, therefore, what size I will be?