I think how it works is not exactly that the UK can force the sale, but they can deny Facebook access to the UK market if they don't follow the rules set out by

I think how it works is not exactly that the UK can force the sale, but they can deny Facebook access to the UK market if they don't follow the rules set out by regulators. It is up to Facebook to decide whether that is worth it, similar to the issue between Google and newspapers in Australia or following GDPR in the EU.