Did I miss something, but the author didn't actually say what it was GCHQ did, if all they asked him for was his contact details, then what's the problem, lots of organisations like to know to whom they are sending information.
And what's wrong with GCHQ checking up a little, after all there might just be a terrorist dumb enough to give valid contact details.
Sorry but I really don't see the point of this story, Ok, there are still classified documents around that probably shouldn't be, but what do you expect the process to be for releasing a document, FOI request for marked document, check marking, no way, check person, end process, you really don't expect the people who process FOIs to go much further than that do you, they can't read the document first, just to see if it's marked correctly.
And take a step back here, and look at the process you would expect a national security organisation to go through when asked for information, to protect you, and them.
The FOI is not a mandatory declassification process.