I guess I don't find what's so difficult. All you need to do is look to Norway. If you want to make an argument that "the last bit is the toughest" - I guess? But they're already well, well on their way to a low emissions strategy.
As for it being impossible for a country like the UK: you're making some ridiculous assumption that the UK would need all energy to be produced on-shore. Does the UK get all of its coal and oil in-country? No? Then why do they need to get all of their energy in-country? If they need to import and store batteries or hydrogen or insert energy holding vessel so be it.
As for it being impossible for a country like the UK: you're making some ridiculous assumption that the UK would need all energy to be produced on-shore. Does the UK get all of its coal and oil in-country? No? Then why do they need to get all of their energy in-country? If they need to import and store batteries or hydrogen or insert energy holding vessel so be it.