One of several. Though the most famous equivalent to Vermin Supreme in the UK is probably Screaming Lord Such (RIP) of The Monster Raving Loony Party. He was a staple of elections in the UK for a couple of decades.

Fun fact: when Such finished ahead of the candidate for the struggling Social Liberal Democratic Party (SDLP) in a by-election, the SDLP officially and permanently shut themselves down. So Such basically caused the death of a legitimate (but failing) political party.

Another UK candidate is Lord Buckethead (of the Monster Raving Loony Party).

As a side note, there have been many one-off UK prank candidates too, like the Alfred The Chicken Party (which was advertising a new video game), and the Mongolian BBQ's A Great Place To Party (advertising a restaurant).