@Gromit
Thanks for putting that old "except when" thing to bed, for now. Saved me some typing. :)
People can watch this in action with regular visits to :-
http://www.gridwatch.templar.co.uk
Over the course of the recent winters, I have *never* seen the oil-fired stations gauge budge. (Hover cursor over a guage for some enlightening background info).
The interconnector guages show inputs from French nuke output and spare Dutch wind ouput. Also, how much we put through to Eire & Ireland.
So the crisis scenario requires a 2010-style Siberian blast (jetstream on the blink again) affecting Eire/NI as well as all of UK, yet no wind over Holland and a glitch with the French link.
But, if roads close with snow, factories cannot run at capcity either, lessening the load.
Surprisingly, the year's peak demand may be in high summer, thanks to the recent trend for air conditioned office space.