Hi undisputed....
I can't speak from experience, I've been RAF through and through. But I would imagine your chances depend on your attitude and the way you come across at your interviews.
The AIB might well ask you if and why you didn't want to be a navy pilot first. If you can explain without bull****ting or waffling (they can smell that a mile off), the sincere reasons why you want to be a naval officer and pilot, I can't see there being a problem...
There might be some navy out there who will say differently, but that's just my perception.
But you must do some serious soul-searching and come up with the right reasons for wanting to join HM Forces as an officer, then convince a selection board that you are their man!
Good luck whatever the outcome