Some of the professional titles that mental health workers use are unprotected in law. In other words, it is not defined very well who can use and not use these titles. This video [here] describes the issue. Whilst there are a lot of professional bodies who accredit therapists, a first step is to check that the mental health worker is registered with one of them. You can then research the professional body to check that they accredit a form of therapy that is known to be effective. All therapists should have a description of their qualifications and the professional body with whom they are registered, detailed within their websites. If they do not, my recommendation is to avoid using them.