Well legally unfair (data breach/breach of confidence) misleading etc is sharing details of reasons for my absence ie "work stress" . And that, in circumstances where "work stress" were not the full absence reasons, and also where I had written in advance saying dont share.
I do think you are missing the point -
(a) you can ask them not to share this information, but you cannot prevent them from doing so, and
(b) legally they haven't shared it with anyone who does not have a right of access to it any - the employer shared it with themselves
To be balanced - and I am trying to maintain a balanced view even though I agree that they are being deliberately vindictive - did you "share" with your potential new (Civil Service) department the fact that you are suing the Civil Service? I doubt it, because I wouldn't have advised it. But that fact would certainly colour the view of many employers about an internal candidate - and whether the job was advertised externally or not, you were an internal candidate.
It's crap, I get that. And it's not fair, I also get that. But realistically your employer has zero interest in mitigating your claim. If they did they would have leapt at the chance to relocate you somewhere else long ago, never mind now. If they have no interest in mitigating the claim, as I told you previously, they are being 150% clear about where this is going, and the only question is about how long it takes. Unless you are very well off (and if you were, would you be looking for a job anywhere?) they can play the waiting game for a very long time. It's in their interests to do so. It won't cost them a penny more to play the long game.
Instead of focussing on the employers games, isn't your time more usefully spent finding out what your lawyer is doing to bring all this to a conclusion, whatever that conclusion is?
And don't assume that OH is "on your side" - they are on nobody's side, and if they are doing their job correctly, they shouldn't be either. They have made a recommendation - the employer has decided not to accept that recommendation. And, as I have also said to you several times, probably on legal advice. It makes no sense to me to want to avoid mitigating your potential claim unless that is what the lawyers are advising them to do. And there is no way that lawyers aren't issuing the instructions given that there is a claim already on the table. Although not Civil Service, I know the public sector well; and once a claim hits the table we are not allowed to breath without legal advice, never mind act.