S. Korea has a block cipher that no other country uses. Almost all S. Korean internet users install a plugin which allows them to browse the S. Korean internet since all S. Korean internet businesses must use that cipher. The UK could require that all companies that wish to do business in the UK must use the UK's CA. This would incentivize users to install the CA and incentivize vendors to pre-install it.
And S. Korea is the only Korean speak country on the internet. The UK is not the only English speak country. Many people will simply ignore UK sites and just use US ones.
