That’s one.
The easy one.
What was the other?
For anyone who would like a clue about the second Czech-born writer:
The second writer is not Karel Čapek, but he IS primarily known as a playwright. The language that he wrote in is English.
A science fiction movie made at a British studio, with a British director and a largely British cast, about a discovered alien artifact which had profoundly affected humanity’s ancestors and changed the course of our evolution, and which is still active today and sending out signals. Released in 1968. Based on a story from the 1950s.
One is obviously 2001 A Space Odyssey. I guess the other is Quatermass and the Pit (aka Five Million Years to Earth).
Barbie was played by Margot Robbie in the recent movie and she’s Australian.
(That said, I saw her in a couple of movies before I realized she wasn’t an American. She’s really good at the accent.)
Good answer! ^^^^^ 
Well, all right. I don’t think it’s Arthur Miller, about whom I know not a lot. How about Tom Stoppard or Harold Pinter, about whom I know practically nothing?
Tom Stoppard it is! (Born Tomas Straussler, adopted by his British stepfather as a young child.)