There are a number of great free online theatre options available for people in the UK. The BBC has put three of its shows up on YouTube for public viewing for free. These shows include the Mind the Gap show, Walk the Plank show, and Emergency Exit Arts show. You can watch all three for free or download the play text. To view the full show, you need to be a member of the BBC.
The acclaimed theatremaker Bob Bye has been creating thought-provoking work for years. He recently launched a Patreon page to raise money for his work. In 2013, the Old Vic Tunnels in Bristol performed an apocalyptic play that is now available to watch for free on YouTube. This production is a rare chance to see the work of a local theatremaker. Using the archive recording, you can watch this performance and many others for free.