For those seeking a therapist in private practice (also some NHS therapists), you can search the following sites:
UK - Private Practice
You can search The Royal College of Occupational Therapists
Ireland - Private Practice
You can search the Association of Occupational Therapists of Ireland - Private Practice by keyword (sensory) and location.
You can search the SIE Association of SI Practitioners' Register. You'll also be able to check sensory integration (SI) qualifications for a particular therapist on the ASIP register.