You’re not getting the point of what I was saying. If he does that, his employer would probably fire him. This is because from a uk company is kind of a nightmare having an employee abroad (it’s different if he’s a freelance contractor)

Sure he is paying “useless” tax in UK but at the same time, this helps to keep his job. The reclaiming on tax could not be as much as the benefit of keeping his current job.

Still, if his employer doesn’t have any branch in Estonia, for them paying taxes on employee behalf in Estonia could be so difficult that he could end up loosing his job.