Thanks all - I agree that I need a lawyer. [modified to remove various details] I absolutely don't intend to allow myself to be declared dead.
[modified various details - short version is that I think the cat is already out of the bag in my mother's professional community, but I don't think she's tabloid fodder]
In terms of whether the charitable work, or her failure to write a will, suggests that she felt some regret: I just don't know. I would never have contested a will - but she might not have known that. To write a will that excluded me in a way that would stand up to a challenge, I suspect she would have had to admit, in writing, that she had had a child - and was deliberately excluding that child from inheritance. [removed various details] Now obviously it's all come out anyway - and maybe she was hoping it would, but couldn't get up the courage to do it herself. Or maybe she was just hoping she would somehow get away with it, like she had while she was alive. Or maybe she knew it would come out, and didn't care as long as she didn't have to deal with it... She didn't die suddenly or unexpectedly - she had a protracted illness that gave some time to get her affairs in order if she had wanted to, so in some sense she "chose" intestacy. But I have no insight into why she would have done that...
In terms of how I feel about it... Many years ago, I went to what I now joke was the world's worst therapist - just wildly unprofessional in all sorts of ways. Weirdly, it still helped - but only because all I really needed was to say terrifying things out loud to someone - a tree stump probably would have done. But one of the things the therapist was fixated on was reparations for childhood abuse - she constantly tried to steer therapeutic conversations into planning for legal action for financial redress. Now, I have no objections in principle to this - not least because there can be ongoing medical bills, as well as financial consequences of growing up in a sucky environment: if people want to demand something financially from abusers, I'm fine with that. But for me, personally - sort of symbolically - I felt like it suggested that I could somehow be 'made whole' for what had happened. And there was just no way that could ever be true - not for any sum of money. There was nothing they could possibly pay me, such that we could call it "even". Again - to be very clear - I don't think this is how everyone "ought" to understand financial reparations: I think there are solid material reasons for people to ask - or sue - for financial redress when they've been harmed, to help offset the costs of the harm. But for me - irrationally, but I feel no motivation to become more "rational" here - I felt like I would be offering a way to pretend they could compensate for the past. And just... this isn't something money in any quantity can do... I'm not sure whether the inheritance falls into this category for me - logically, it would be hard to think anyone would view an intestacy proceeding as a form of amends - but I am not clear how logical I am going to be :-)
In terms of stepping in to prove that I'm alive, but otherwise refusing the inheritance: if I refuse the inheritance, I think it then just flows to my kids... I'd need legal advice on how this would play out, but my impulse is to protect them from being drawn into this whole mess. I agree that I don't actually need to make any decisions right now - I just need to prevent myself from being declared dead. I'm just normally a planner, and I was startled by how much my mind just baulks at thinking beyond the "I'm alive" step...