Britain can’t rely on France and Ireland to keep the lights on
Just like Germany can’t always rely on Belgian and French nuclear power, Polish coal power, and Austrian hydro to keep the lights on. All European countries have pretty much used up their own flexibility and need whatever they export for themselves now. Those who have always exported their own inflexibility face dire times. I expect European network interconnection to be rolled back in some way in the future. Power nationalism is on the rise. Thats what wind and solar do.