Looks like the article on the-scientist summarized the relevant study incorrectly. The study itself posits 3.1 million deaths averted across 11 countries in Europe, not just in the UK:
> We find that across 11 countries 3.1 (2.8–3.5) million deaths have been averted owing to interventions since the beginning of the epidemic.
A bit concerning though that the second paragraph in the the-scientist article made such a significant mistake in summarizing the research.