They arent going without. Blackouts/brownouts are exceptionally rare in the UK.

That's fine for residential customers. But if there isn't cheap, reliable excess capacity then that inhibits industrial growth. Low economic growth rates cause everyone to go without.

That's not the only way to go without. Cutting back on your electricity usage because your utility bill is getting too high is another way to do it.

Sometimes that's fine if you're just reducing waste. However other times it could mean that you can't keep your house at a reasonable temperature because you can't afford to run your heater/air conditioning enough. That's a form of going without.