The problem isn't "there's no sun in the UK". The problem is: What do you do on an overcast December day with no wind? Or worse - what do you do if the whole co

The problem isn't "there's no sun in the UK". The problem is: What do you do on an overcast December day with no wind? Or worse - what do you do if the whole country has heavy snow and no wind in December? Renewable capacity factor isn't predictable on a daily basis. You need a backup - which basically means having an entire grid's worth of gas turbine/coal/hydro plants in storage for a few hours a year, or having grid-scale storage. That's not really a solved problem (even the biggest batteries are a couple of orders of magnitude too small to provide an entire country's electricity supply). Electric vehicles (with vehicle to grid) will help. But even then, we need way, way more long term storage than we currently have.