The episode was plainly a stunt.
…
Other footage included some pretty full on vitriol constantly being shouted at the official counter protest
Part of the difficulty is that individual does routinely claim their actions are as a “private individual” yet they run a campaign group and their private actions frequently appear to be filmed by people in an entourage.
They do not claim on these occasions to be “demonstrating”. They are, therefore, not authorised to demonstrate and they have not discussed policing arrangements and other security and crowd management arrangements.
There are often official parallel-demonstrations. (As abarro81 points out, it’s not clear if it’s sensible to call these “counter-demonstrations”; probably more anti-specific-demonstration demonstrations?) At these, the police do attend and they have investigated incidents of hate crime, intimidation, etc. (Even if there are not arrests, people may be warned and/or records made on the Police National Computer.)