Yes, it turns out Peter Firth wasn't just trolling us all for kicks (though he probably was a bit), there is an actual, genuine Spooks movie in the works.
What we know so far:
1. It will be called The Greater Good
2. It will star Kit Harrington and Jennifer Ehle as well as Peter Firth (who will apparently be the only TV cast member returning, sadly)
3. It will be directed by Bharat Nalluri
4. It will be written by Jonathan Brackley and Sam Vincent, who wrote most of series 9 and 10
5. The plot goes something like this:
'The story revolves around terrorist Adam Qasim escaping MI5 custody during a handover to the head of counterterrorism. When Pearce vanishes, his protégé Will Crombie is tasked with finding out what happened as the clock ticks down to an attack on London.
Crombie eventually uncovers a conspiracy that runs from Vietnam to the Mediterranean'
Sources:
http://www.digitalspy.co.uk/movies/s120/spooks/news/a528064/spooks-movie-the-greater-good-to-shoot-in-2014-plot-details-revealed.html and
http://www.digitalspy.co.uk/movies/s120/spooks/news/a529572/spooks-movie-casts-game-of-thrones-kit-harington-jennifer-ehle.html Thoughts?
(be impressed at my lack of capslocking; I'm saving that for the comments)