whenurhappy
I suspect that the CPS selected the corruption in public office charges rather than ones from the OSA to avoid the public interest 'defence'.
I think you are correct. Given one of the subjects was kit shortages, I'm not sure the raft of Ministers who lied about this would care to be called as witnesses.
On the other hand, these shortages and lies were well-known, so it seems odd the Sun would pay for the information. I'd speculate they wanted to get their hooks into a source.
If she hadn't taken money, she'd have been fine. That she now profits from selling her experiences is beyond the pale. But she's in good company. A raft of Ministers.....