Actually in England at least at the time of Prince Charles´s engagement, everyone knew of the Spencer family, Lady Diana would have been immediately recognized as a member of that family even if not physically recognized, they are an old aristocratic family closely related to the Churchills, who have been part of British history for so long that everyone who is a "native" knows who they are. Although I did hear someone with a British passport say, at the time, she must be a daughter of the Spencer from Marks & Spencer´s store people.
I think this whole "courtship" has been handled very badly, by Clarence House, the Press everyone. If he marries Kate Middleton I think they will be a very uninteresting couple, no substance, and the republic will be well on its way. If he doesn´t, after all this brouhaha he is going to be considered a cad, but he is royal, he will get away with it, if anyone is left crying it is going to be Kate.