In the British Jeeves and Wooster ITV TV series (1990-1993) with Hugh Laurie and Stephen Fry, does Wooster ever—or indeed frequently—say “Don’t you know?”, like he frequently does in the books? For example, “He’s my butler, don’t you know?”
The line is one of the most endearing things about Wooster and is quite important to some people who like authenticity. I watched the first two episodes but alas I heard no trace of this line.
Also, a Google search reveals only two episodes where it is employed.