Still one aluminium smelter in Scotland:

https://alvancebritishaluminium.com/

Which has it's own hydroelectric scheme:

https://en.wikipedia.org/wiki/Lochaber_hydroelectric_scheme

Aluminum smelters have so high electric consumption that you usually build then near the cheapest reliable sources of electricity.

Cost of electricity is a very significant part of production costs of aluminum, around 30% on average.

https://www.aluminium.fr/en/energie