Great summary here of the kind of things people are arrested for and a bit more about the laws this refers to https://open.substack.com/pub/monkdebunks/p/are-30-people-a-...
Here's one horrible example:
https://www.bbc.com/news/articles/c0j718we6njo
As an aside the police body cam footage one of the officers searching his house says "lots of Brexity books'
There are countless awful examples of arrests for online comments. Here's another:
https://www.bbc.com/news/uk-england-merseyside-43816921
She posted the lyrics of her dead friends favourite rap song, and was convicted. How this even resulted in an arrest never mind court and conviction is beyond me.