Oliver Cromwell (and son) would appear to be the only proper Englishmen ever to have been in charge of the place.
Roman Emperors: Various ethnic backgrounds. Hadrian was Spanish. Constantine was at least born in England.
Alfred the Great to Harold: Saxons, invaded in the 6th century after the Romans had vamoosed.
Cnut etc: A Danish interlude. Invaded 10th century.
Normans: French-speaking Norwegians, invaded England (amongst other places) in the 11th century.
Plantagenets: Anjevin French, from 12th century to end of Middle Ages.
(Oliver Cromwell...and son)
William III and Anne: Dutch
And after George I it's Germans all the way.