All this was foreseen as long as twenty years ago, and has been highlighted to government with increasing stridency pretty much ever since. Sadly, politics is a short-term game for most, and it's been easier to kick the can down the road.
We've failed to replace nuclear capacity as it's gradually reached the end of it's life and gone off-line (what's left is currently being flogged flat-out). We've pinned our faith on inherently unreliable and pretty well uncontrollable sources like wind and solar, and shut down reliable big generators (coal) without replacing the capacity. We've built some efficient gas stations, but arguably not enough. If we lose a big station to breakdown in the next three months or so, we've got an even bigger problem.
There are some emergency fall-backs. There now exist some small companies owning banks of diesel generators paid to be on standby - and paid very handsomely if their capacity is called on. As highlighted above, big users have been 'incentivised' (read 'punished') not to use juice at peak times.
I'm amazed the MSM are not reporting this. I can only think that the likes of the BBC daren't because it highlights the consequences of their climate change agenda.