One interesting advantage for UK buyers of gold coins specifically, is that if they're legal tender they're exempt from (Capital Gains) taxation[0]. Even if the gold content is worth significantly more than their face value, which is almost universally true.
This reminds me of the guy who paid his employees in silver dollars and paid taxes on the nominal value paid instead of the market price. He also ran a separate business that bought all the silver dollars back for the market price right next door.
It all went well for him until he started a payroll company to do the same thing in multiple states.
[0] https://www.royalmint.com/invest/bullion/discover-bullion/ca...