I wondered if I am wearing the right size bra so looked up the instructions on how to measure and one set said I was 36F and another said I was 40B. Really?????
The Wikipedia article was actually quite good about how difficult it is to get a sensible measurement that really works because, of course, everyone is actually a different shape, and breasts vary in shape a great deal as well as all the rest of one's anatomy. But the bra manufacturers aren't taking that problem on board. If you are very well off and can go to Rigby and Peller they don't measure you, they look and you and then get a bra to fit. I have a friend who did get a bra from them but they cost the earth and they tell you that you should get refitted every 3 months!!! £100 on a bra is not in my budget.
So for more normal mortals we just have to keep on buying bras that sort of fit. The one's I have found most comfortable are actually really cheap ones from Tesco, but I suppose if I was prepared to pay £25 or more each I would find other comfy ones, but it goes against the grain. I have had some expensive (ie £25 plus) bras but they are not appreciably better than the cheaper ones.
So I went into M&S and tried lots on today, lots of different sizes and shapes, and came out thinking that the size I am wearing is probably the right size actually, and that M&S bras just don't fit me.