I have no idea what the protocol is for naming an heir to throne of England. I assume that Prince William and Kate Middleton are free to think up names as they please, before the queen walks in with a terrifying grimace and her dumb corgis and politely tells the couple that none of their names will ever do and that the baby must take the family name Edgurt. And then the queen strolls out of the room and the corgis scamper off to lick their balls and Kate tells William that she can't wait until his grandma is finally dead and buried. Then they argue and later have makeup sex on a pile of emeralds. That would seem to be the proper British way of doing things.
But while the happy couple may be forced into a formal name they don't care for, that doesn't have to stop them from CALLING the child any nickname or pet name they see fit. My first choice for the child's name is, of course, DIANA. Girl or boy. Just to really stick in the queen's face. "Here, here's a living memory of the woman you so callously slagged, you granite harpy."
But there are other options as well. A quick glance at the most popular baby name in the U.K. suggests that the British aren't nearly the colossal failures at baby naming that we Americans are. Why, there's nary a Jayden to be found on the list (though there is a Maddison, which is troubling).