pegasus, I have a PhD degree (not a certificate--we don't have those here), so that means my title is "Dr.", but that doesn't mean I am a doctor. Here in the U.S., being a doctor means being a physician (MD). But anyone with a PhD (or equivalent professional degree, such as Doctor of Dentistry or Doctor of Veterinary Medicine, or whatever their degrees are called) can be addressed as "Dr." instead of "Mr.", "Ms.", etc. I seem to remember you are in UK? So the convention could be different there. When I lived in Switzerland, we called the male professors with PhDs there, "Herr Doktor."

Dr. Sunny