I'm not a music therapist but I know people that have an interest in/are studying music therapy.
The people I met had degrees in music. Music Therapists are 'Allied Health' professionals (i.e. those that are not Doctors or Nurses (or HCA's)) which means that regulation is complex. I would get in touch with a professional body and ask them for routes into employment. The list of musical experience is, sadly, irrelevant - they want to see hard qualifications (that aren't about your musical ability) so I would contact the professional bodies involved.
That may be of some help.
My family work in Healthcare (as have I in the past) and I can't even begin to explain how complicated a lot of the bureaucracy is! I was a professional bureaucrat for each summer for the last few years! Good luck with your search.
EDIT: Also useful: