Perhaps you should think about also looking for English-American celebrities to do likewise? After all, Merian C. Cooper was English-American.
I do not doubt that there is a load of respect for Mr. Cooper in Poland.
However, by clearly established forum standards, he was an American. Period. After all, being one or two generations removed from ole blighty, there would be no connection of any value by which he could claim to be or claimed to be British. I am sure he would have been calling is own mother "mother" not "mumsy".