>UK comes from three main sources – gas, coal-fired power stations and nuclear. A small but growing proportion of electricity is supplied by renewables.

That's not really true anymore. Wind power supplies double that of coal in the UK. It's gas, nuclear and wind with coal coming in 4th. Check out http://www.gridwatch.templar.co.uk/ for live figures.

You also have to think about when they will be consuming electricity, which will primarily be at night (taking a reasonable guess here) where the balance of wind and nuclear is even higher.