Basically look in your yellow pages and phone around its the only way your likely to find out!!! I assume you dont want to be paid more of rides in return or just working for experience???
i have phoned a few places but they wont take me. I dont mind if im paid although riding would be nice i just want to learn the horse care side of things as i have never learnt any of that just riding.
Health & Safety is such a problem in riding schools now its a lot harder to do this than it used to be (I know because I work in A riding school where pickle is kept on livery) I think you just have to hope persistance pays off. good luck