Nope Sorry.

A GB news presenter is not all reformers, (yet)

Added to UK law on self defence is very anti predictive risk as a motive. You would be required to show the reformer had a gun or some other intent to harm you. More accurately that you had reasonable cause to feel threatened.

Now if reformers actually started doing so. iE you had evidence that GB news presenters had been successful in inciting such attacks.

You would still need to show evidence you though the reformer was going to attack.

So no shooting random reformers presenting no evidence of holding a weapon or aggression. But you would have a much easier time convincing a jury etc that you thought his fishing rods were a riffle.

I hope this advice helps with any decisions you may be forced to make.