Sure, but if the fine is non trivial, Microsoft could file a lawsuit. It would also be a bad look for Britain to effectively extortionate foreign firms to keep

Sure, but if the fine is non trivial, Microsoft could file a lawsuit. It would also be a bad look for Britain to effectively extortionate foreign firms to keep doing business in the country. Whether it's called a "legally approved levy under xyz law" or a bribe to the government is beyond the point. It's the kind of thing you see in corrupt third world countries.