The fact her husband was a bigamist and a con man would not have been covered by the official secrets act.
I also felt Alex was portrayed more sympathetically than Alison, he was portrayed more as the nice well meaning guy who made mistakes. Maybe a walter Mitty,
I doubt any of the women were unpleasant in real life. It was likely Alex was the unpleasant one, but like any conman had a level of charisma. It's interesting his wives simply got younger and younger, he lied through his teeth to them and his kids, and he pretty much left them destitute.
The fact information about him is still classified will be more about intelligence work and what he uncovered during his employ with the intelligence services.
I was reading an interview and one of the family said many of them were hoping the info withheld exonerated him, but. He can't be exonerated from the fact he was a bigamist, a liar a cheat and a conman, a criminal also, and as such I'd suggest it's highly likely he was highly likely he was fired from the intelligence services for what they say he was fired for.
They will be withokidjnt information not because it would prove him guilty or not, more it will be about security issues.