"Or the less favourably, the Tories don't implode and quietly don't invoke Article 50, we get to 2020 and the North of England votes for UKIP, Scotland votes for independence, and the Tories continue to run the country just has they have been for the decade before."

I'd love to be wrong, but I think this is the most likely scenario. Intensified by Labour melting down in England the way it did in Scotland, and almost certainly becoming a rump in our increasingly right-wing country.