...but I do need to point out that 12% of electrical demand is about 1800 ktoe, which is only about 1% of total energy demand. We use about six times more petroleum energy that all electrical demand put together.
Scotland already went through a period of energy resource shortage in the 1800s when there were very few trees left. Going back to only locally renewable resources might be like that again.
Tide is one of the few renewable technologies that generates reliable power, and so is suitable for baseline load. Even in Scotland, the wind drops. But it's had very little investment, partly because of a poor reputation from horrific ecological damage caused by tidal barrages in the past, but mostly because wind is sexier.
But plants big enough to actually make a difference are going to be very, very big. Microgeneration is great for small rural communities, but we live in cities these days.
Here's a new 320MW tidal lagoon being built in Wales: http://www.tidallagoonpower.com/projects/swansea-bay/ These only work when attached to a coastline, though.
No, that's the big mostly offshore wind farms. Currently sitting at 12% of demand: http://gridwatch.templar.co.uk/
Energy independence on the personal level is as much of a pipe dream as economic independence. You might be able to achieve it at great expense, but what for? Even on Eigg the islanders are on a little grid.