I'm not entirely positive on this and would welcome clarification from a UKer, but I think thier arresting is much less consequential than ours, really little more than a formalized questioning. Last couple times I was arrested, I was cuffed and tossed in holding while I was given one shot at making bail before going to county. The UK concept of arrest is kinda genteel.
Eta: this guy was not fined, cited, or charged, and no restrictions put on him. Near as I can see, it was a strongarm questioning about possible hate crime activity. Not exactly Thoughtcrime territory.