Just aluminum smelting all moving to China probably reduced UK energy consumption by a few percent.
We import very little Al from China; it turns out mostly to come from the UAE, which will have absolutely terrible CO2 emissions, as well as greener countries like Iceland and Norway.
It looks like we need to invest in local recycling (which, yes, needs cheap energy, but not as much as primary Al) in order to make more of a circular economy rather than just exporting vast volumes of scrap.
https://alvancebritishaluminium.com/
Which has it's own hydroelectric scheme:
Cost of electricity is a very significant part of production costs of aluminum, around 30% on average.
Consumption of final products, and exports are what make more sense to look at to see if lives are better today than the 1970's, which the article implies it isn't.
There are still electric arc furnaces in the UK and more are being built