OK, emotional rollercoaster slowing down now I hope.
The e-mail came. HoD came up with, not a jobshare, but an arrangement - my current teaching is also used by History, I get some courtesy title such as associate or somesuch in History, and this is for the remaining 18 months of my fellowship. I also get a salary topup, and History is finding the money to jointly do that. I am to develop a certain MA course, jointly with both depts; and I can do bits and pieces of teaching for History.
So, right now I have: Law keen to keep me; History keen to have me (but can't just create a job especially in this climate) and willing to stump up cash for me.
This is good.
In the future: at the end of my fellowship law have to advertise a post I can apply for. (No guarantees; I know that.) When that happens, and if I get the job, History will look to co-fund a position for me, and make further use of me.
Also good - I have this on paper.
The negatives - it's not as good an offer as Aber, it's not secure, and I've now turned down Aber. I cried on the phone telling the HoD there , and he told me he was gutted. But he's a lovely man (argh! Why couldn't he be a shite? There's loads of them in academia!), totally understood my reasons, wants to work with me asap, and will be on the lookout for me in the future.
That's the hardest thing I've ever done in my entire career. I am totally and utterly shaken and emotionally drained, but I'll bounce back and be a nice mumsnetter once again. (Btw, I'm aware it's pretty minor in the scheme of things, but just for tonight it's my big thing.)