I know a good bra can transform an outfit and I know I have some that are better than others.
I have a very small bust, 34B according to M&S but even if that's wrong, I don't really have much to put in a bra. e.g although I do wear a sports bra, am perfectly comfortable running in an ordinary bra, there really isn't much to bounce!
So, what (for me) would be "a really good bra"
Also, while we're on the subject, tell me about fancy bras. I always buy completely plain t-shirt bras as I find any lace or embellishment just makes lumps under my clothes, but clearly a lot of pretty bras are sold, so what do others do?