I am sure that one couple is all they can take. Its in Westminster Abby which is not very large. Mandela had his funeral in a football stadium.
I assume that Harris may attend in the President’s stead. Leaders of state from around the world will be invited and likely will fill the Abby. But only close friends and Family of the queen are likely to take the other spots. No George Clooney or past Presidents.
No Elton?