I must again say there's a lot of ignorance going around about English leaders:
Richard the Lionheart
As I've said before, he visited the country TWICE. To collect TAXES. He wasn't a leader by any strech of the imagination. and, as someone else said, he was French anyway.
Henry VIII
Erm... Lolwut? Sure, the Church of England was created in his rule, but that was the only lasting influence he had, and religion isn't even in Civ V for Diplomacy (which was pretty much what the CoE did)
Victoria
Yeah, she may have been queen during the peak time of the Empire, but she was an incredibly bad queen to be honest. Once Albert died she never showed her face in public again- by that time in History, the monarch of England had almsot got to their current 'figurehead' status, but Victoria was bad as a figurehead as well. If we want an Empire-Era leader, take Gladstone (for goody-two-shoes factor) or Disraeli (for expansionism).
George III
Yes, it was under his rule that America gained indepenence. But his only other defining factor was that he was Bat**** INSANE. If you haven't noticed the leaders tend to be competent.
Henry V
Ok, if you REALLY want a guy who was famous for winning one battle and then died, go right ahead. But that was all he did...
My personal choices would be:
Gladsotne/Disraeli (for the Empire, leaning towards Disraeli because he was slightly less boring)
Churchill (Only if you want to emphasis the whole 'British Stubborness', he would have to come with an ability like that, perhaps making English cities much harder to subjugate)
Lloyd George (He was Welsh. And he was a womaniser. And he was at the Treaty of Versailles. 'Nuff said)
And if you really want a Military-Minded guy:
Oliver Cromwell (Britain's first, and arugably only, Military dictator)
Oh, and for pity's sake, just change the name to Britain.