Are you in London? Because if you are, you will be spoilt for choice; if not, it's a bit harder.
I went through this a while ago (in London), and so, sadly, can't remember the details. But I went through one of the organisations who gave me an assessment session (I went and met a lovely older woman, and told her why I thought I wanted therapy etc) and they then recommended me someone - but said if I didn't like her, to come back and they would recommend someone else. As it turned out I liked her very much, and I saw her for a couple of years and it made a huge difference to my life and I can't recommend it too highly.
This might help. Not sure if this was where I started, but it looks like it.
Perhaps one way to think about what you want is, what kind of therapy you are expecting, and what you want from it. Are you thinking of open-ended, 'classic' therapy for a couple of years, or do you want something more results based and shorter term? Is there a particular issue or phobia that you want to deal with (in which case you might want to find someone with experience of it) or a more general reassessment of life.
Fwiw, incidentally, my therapist, although v old-school, never ever sat back and thought about the weather, she was always challenging me and jumping in and so on!