:::::::::one way to deal with that is a parenthetical (or Lech Walesa) - but that's essentially insulting the reader's intelligence, in that it assumes that a reader is too stupid figure out that the person named Lech Wałęsa is the same as the guy named Lech Walesa they might have encountered somewhere before. The Britannica link is right up there, and as far as I am aware that's a English language, reliable and comparable source. So by that standard, Lech Wałęsa, IS English. 
 :::::::::Oh, and by the way, I seriously doubt that "Lech Wałęsa" "has been written in the English alphabet (anglicized) for more than 40 years in RS" as "Lech Walesa". While that's not quite impossible, the chances of it being true are slim. Hence, you're making stuff up. Ah, Wikipedia.