KARL
For what it's worth, I think the likely consequences of Brexit will include breakup of the UK, collapsing living standards and very likely a considerable level of employment. In other words - a serious economic crisis, which is bad for everyone. But I don't think that Leave voters have voted for that because it's what they want to happen, I think they disagree with the idea that it will and actually think the country will prosper. So I'm not sure the vote represents a deliberate act of self-harm, even though I think it will prove highly destructive. But in any case I think the society of Britain will survive it (even if the political entity of the UK doesn't).
It's a bit hard for me to put into specifics what I think would happen if Brexit were to be somehow reversed now. It would certainly be less visible in the short term - I don't think the UK would break up, and there'd certainly be social unrest, but that would recede. I suppose what I think would happen is that the whole political culture of the UK - the culture of political engagement and, I suppose, basic belief in the idea of parliamentary democracy, would be permanently undermined and replaced fundamentally by cynicism. I'm not entirely sure what that would look like or how it would change this country, but once that kind of rot really sets in it is essentially impossible to remove. I think we'd have very, very dark days ahead of us in that instance.