My gut level response is to say a bit of both.

Has Al-queada, faced with a more active opposition, been forced to reorganize and refine its efforts? Certainly. This "effect" is no different than any "army" in history. Once they've been through a few fights, they learn what portions of the peacetime routine were wrong. So while I'm sure there is a good deal of truth here, this is hardly a surprising development (unless our terror-fighters are complete idiots, which I trust they are not).

Britain as primary target? A little fear-mongering mixed in, no doubt (is it funding/budget time over there?). On the other hand, not without some value since British Government support for the WoT and the USA is a good notch stronger than British Public support for same. If they were to engineer an attack or two that de-coupled the USA and the UK, playing on that difference, it would be a coup that made Spain pale by comparison.