Re: non-UK legislation
Nope, the Eel meant like any transposition of GDPR into an EU-country national law, which could apply to a UK public service if said service failed to protect the Personal Data of the citizens of this country.
Trying to find an example: say HMRC holds financial data for German residents who happen or happened to be UK tax residents, and that data is leaked. Germany's Data regulator could impose a fine to HMRC. That would be UK taxpayer money going to another country's public finances.