I´m not british and I don't live in GB but from what I've seen when going to GB or from tourists around my area, generally, British guys tend to be quite attractive or normal whereas British girls have an absolutely **** style (I'm not saying all of them) but they don't know how to dress well, as in they dress quite trashy (I don't mean to be rude though) which affects quite a lot the general view on their attractiveness.
But all this is a matter of what part of Britain someone is, for example, my brother is a student in Durham and from what my family has seen, the girls there tend to look better than in Newcastle due to the way they dress.