There is an act, I forget what it's called, that prevents Catholics or anyone of a religion other than Anglicanism from ascending to the throne. Although, I was reading in the newspaper that apparently Charles' people are preparing for her to become Queen one day probably in opposition to the present Queen's wishes.
That being said, I would rather replace our head of state with an elected one (preferrebly once every 5-10 years). Why should we be ruled by these rich, sometimes insane, and in-bred people?