While it is true that people (besides the very rich and very desperate) usually don't try and migrate to escape laws, corporations do it all the time and think about it proactively. It is particularly easy for technology companies to say, great I'll do all my hosting in Uruguay instead of Britain, make my terms of service under Uruguayan law, etc.

If Uruguay becomes a criminal sanctuary--then sure maybe it will be ostracized internationally--but as long as law abiding, upright business people have legitimate business there its more enlightened policy will make others think twice about enacting less enlightened ones and give companies some options. Moreover, it gives companies tied to Britain a strong incentive to advocate for a reasonable policy so they are not placed at a competitive disadvantage.

This doesn't mean that lawmaking has to be a false choice between anarchy and totalitarian surveillance, just that the OP's point that more variance in jurisdictions, the higher the pressure on the least permissive to mitigate the worst excesses is a real phenomenon.