CS Lewis was an Anglican.
It was Tolkien who was Catholic.
Hmmmm....as near as I can tell in researching Lewis' writings, Lewis argued about free will in The Problem With Pain. That's as close as I can find on this subject. It is not considered one of Lewis best works but that may have nothing to do with his argument on free will. It is one of his earlier works. I do remember reading the book many, many years ago but I no longer have my copy nor do I remember the book.