Not sure, but before I indulge in any further hyperbole, the Paul Chambers case, referred to as the Twitter "Bomb Hoax" case, would also be covered by the Criminal Law Act 1977. So, although the Tweet that Chambers was arrested for was a "bomb hoax", he wasn't convicted for perpetrating a "bomb hoax".
This article puts it better than I could:
http://www.thelawyer.com/the-twitter-%E2%80%9Cbomb-hoax%E2%80%9D-case-worse-than-we-thought?/1003651.article
This thread is straying somewhat from the OP, however, I suppose my discomfort with this article of law is that it is, like the Terrorism Act 2006 , being used as a catch-all to convict people of offences that exisiting legislation exists to enable prosecution but where the onus of providing a body of evidence is too taxing for the CPS.