I'm surprised those who have complained about lack of Britain in this thread haven't complained about the leaked leader choice yet,
.Spoiler :Ada Lovelace
Personally I'm not that excited for her solely as I wanted a royalty who could double as a Norman leader as well. And there has famously been British Queens so it's usually an easy pick.
The two most famous English Queens have of course been done to death at this point, and I’d have been very bored to see either Lizzy or Vicky again.
Of the rest I don’t think Anne or either Mary is a great choice. Eleanor was an inspired medieval choice. Matilda would fit here too, but is most famous for the huge war to oust her. Emma of Normandy or Æthelflæd would be my favourite early medieval picks, but I guess they lack name recognition and would feel quite disjointed from a modern British civ.
So actually I am quite happy to have a non-royal leader, Britain has many suitable options. Ada Lovelace is a good way of representing science and modernity.