Sure it has.
But democracy is very electorate-dependent. The country got every right. But it's electorate has the final word. I say, 90% would value their social networks over their country's right "to impose whatever fees for restrictions they choose".
And these "Multibillion-Dollar Fines", what percentage of their business (and profits) would that be?
It's the matter of policy. If they bend too far in UK, they'll have to bend all over the world for sure. If they cut their losses in UK the chances are good it actually would be a singular case. And there is always a chance that UK would try to pay damages to have 'em back too.
If it's just a singular event they may still just shut down their operations in UK and formally ban UK access. It isn't their responsibility if someone goes around by anonymous proxy.
https://disqus.com/home/channel/newsviewsdiscussions/discussion/channel-newsviewsdiscussions/its_serious_this_time_multibillion_dollar_fines_could_hit_facebook_google_uk_warns/#comment-4359061701