If you want to start at the beginning I would discount the silent era as more specialist, but you will need to include some of the Ealing comedies, Lavendar Hill Mob, and I'm Alright Jack spring to mind. You might also like to include the earlier Pink Panther(s).

There are DVDs of Yes Minister and Yes, Prime Minister, which are a great way to get to understand Britain. They may also atune your friend's language skills to subtle shades of meaning that no class could hope to cover.