I'm with those who hate bras and wish I didn't have to wear one (sometimes I don't but it's not a pretty sight.)
Why can't M and S synchronise their sizing? Even in the same style, the sizes differ. And why do they have them in those awful boxes that fall off the rack as soon as you look at them? They seem to hang them in such a way that you can't see the size unless you move some of the boxes and then they all fall on the floor. Grr. I refuse to pick them up when that happens.
I once had a bra fitting in M and S and it was completely useless. I came away with two bras which, when I tried them on again at home, did not fit me at all so I had to take them back.
Another time I had a fitting in John Lewis in Watford by a bad tempered woman who made it plain she hated her job. This time I came away with two bras that were much too tight. It was too far to take them back so I made myself wear them but they were so uncomfortable they did not last long.
After my recent op my daughter suggested getting some of those all in one bras that are advertised as being the most comfortable bra you will ever wear. DD said I needed a Medium (I'm a size 12/14) but I insisted on ordering Large as I can't bear a tight band round my middle. When they finally arrived through the post from Debenhams I tried them on and, blow me, even the Large gripped my like a vice so they will have to go back, too.