A couple of points just ot keep the pot boiling. When Henry VIII was given the title "Fidei Defensor", as far as Pope Leo was concerned, there was only one "Faith" and Henry got the award for his article attacking Martin Luther's teachings. So the use of the term "Defender of THE Faith" is strictly the correct one.
As for being the heir to the throne, that "privilege" only happened by sheer luck if you consider the murderous records of previous monarchs for example those who did away with Richard II and Edward II. Also if I remember correctly there was a programme on TV some time ago which proved that the real king is living in Australia.
Incidentally in a recent poll conducted by ITV 69% felt that Charles should not marry Camilla.