I agree, do a search on Doula UK. In fact, when I was looking for a doula, most of the ones I found were trainee (mentored) doulas. They seem to be incredibly hard to find just on a Google search, but the Doula UK database is pretty big. You might also find a doula training course if there is one nearby you and ask if they keep a list of doulas they have worked with that you could contact. In my experience, everyone I got in touch with seemed to have been trained by the same person, so that person would have been a great resource if I had gotten stuck in finding someone. Also, look for newly recognised doulas, so ones who have completed training but are just starting out on their own. My doula falls into this category and she was only £200, which even that probably could have been somewhat negotiable.