Dirty bomb threat real

[Scythe13]

There are loads out there that can cause chaos, and loads that want to.

I put it down to a process of elimination.

Neo-Nazi's, semi organised, but are not too bothered with the average Brit. They're more interested in their war and wouldn't effect the typical UK citizen (I'm not supporting the Nazi's by the way)
White Supremacists, same as the Nazi's, but less organised. Again, the concept of collateral damage would stop them doing such a thing. They're more likely to bomb a school or Mosque.
Animal Rights....I'd be stunned they'd do that. Could see them blowing stuff up, but couldn't see a dirty bomb being used.
Anti-Nuclear....Yeah, I could see them doing that. As a way to 'Show the dangers of nuclear waste'
Lone Wolf...not sure about this one. If a doctor or whoever has access to the radioactive crap, goes nuts, I could see that happening.