the question is, where there power cuts, the grid is not a sink to pour lots of power into if there is no power used. It has always been a balancing act to match power generated to power used with, in the past, coal fired power stations kept on line, gas and oil shut down first, as they are easier to ramp power up and down and gas turbines used to generate quick boosts of power, as they could be run up and down quickly although more expensive. with modern methods of power generation, things must still be the same, most cost effective and hardest to shut down would stay on line whilst less cost effective and easier to shut down go off line first.
After denationisation of the power generation and distribution things are probably worse as now costs are set by the various companies who own the power generation companies.