TV Tropes claims that the Monks storyline on Doctor Who (seen in "The Pyramid at the End of the World," etc.) is an allegory for Brexit:
...the actual Who Brexit allegory story (the Monks trilogy) is somewhat less on-the-nose
A brief search doesn't seem to turn up this connection, however, and I don't see the thematic analogy. For example, there's no exit from any organization—if anything, Earth enters an organization. There's a theme of revisionist history, but it's very broad. And so forth. But perhaps the themes are more subtle.
Is there any evidence that the Monks storyline was intended as an allegory or metaphor for Brexit?