My impression is that there wasn't all that much elite emigration out of England, except Puritans in the 1630s, Tories in the 1650s, maybe top farmers to Rhodesia. The country that really got hammered by top talent outflow was Scotland, much of that to England.

England's Dr. Johnson told Boswell, his Scottish biographer of genius, "The noblest prospect a Scotsman ever sees is the high road to England."