I haven't really appreciated the total despair that a nuclear war would bring, until I've seen a report that UK burn wards would've run out of space and supplies within HOURS and would simply be unable to treat even a tiny percentage of the burn victims they'd receive. I imagined hundreds of thousands of people with horrible burns camped around hospitals, just waiting to die, too weak to move or even lash out in rage.
Its worse then you think then, because hours very optimistically assumes any burn wards are left standing. Also since moderate levels of radiation depress the immune system so effectively, the resulting infections would be much worse then they would be normally even for someone who got good care by peacetime standards. The UK though actually got a lot further hardening facilities and stockpiling stuff then most nations did, but it was largely given up by the 1970s once nuclear war no longer seemed so certain to actually happen and old supplies started to need replacing.
They'd be powerless, their government would be powerless...even if they had the most noble, selfless leaders in the world, they'd still all die.
Government? UK civil defense planning actually assumed such total destruction that control of the country would have devolved to a series of regional commands, five or six as I recall. The government as it had been known would not even exist. It did have a bolt hole to flee into given a chance, the huge tunnel complex built into the Corsham Quarries as an aircraft factory in World War Two, but it presented almost no protection against even a weak nuclear attack and more or less existed a decoy, though it had some value in a conventional war as a communications and computer center. Certainly it was nothing like the (limited) protection provided by Raven Rock or Mount Weather. The Germans also managed to build a huge government bunker that could hardly withstand conventional let alone nuclear attacks in a couple abandon railway tunnels. Europeans like functionally useless bunkers I guess.