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Result - This isn't quite how I imagined events, but I'll settle for what's on the table, particularly because I don't have to put my hand in my pocket to achieve it.
Having decided to pursue all matters via the civil route, encompassing all breaches of various contracts involving the tenants and the managing agent, a shot was fired accross the bow of the legal department of said agent (high street household name) to see what they had to say. Whilst our case to them was not unreasonable, it was robust and sufficient enough to provoke a swift response. Very swift, in fact.
I won't reveal precise content, but I think their offer is reasonable, in that it adequately covers restitution, which is really all I can ask. I think they understand quite clearly that I am not wanting to make a profit, but importantly that they are as much at fault as the tenants and that I might seek to cause them public embarrassment if they were to contest matters.
After several telephone calls from senior management, and the like, I will receive appropriate paperwork by the weekend - apparently! It's worth noting that one caller uttered, "ex-gratia" and "gesture of goodwill", though it wasn't mentioned again and he was sent packing with a sore eardrum. Pillock!
I saw matters in court being bashed about, but it's not to be - shucks! (Sorry, DH, no case law this time)
It goes to show; make a nuisance of yourself; state your case, but be reasonable.