Funnily enough, I'm an econometrician/statistician so I understand the role quantatitive analysis.
Firstly, the article is not a technical report. Its a peice of journalism. Its using some basic statistics to thread a report together.
Secondly, in reference to the death in Leeds the author makes the assumption that national figures are likely to be of similar proportions to the London figure.
Thirdly, it offers no descriptive statitics so you could make a relevant comparison even if it were comparing like with like.
If you're going to split hairs over statistics then do it with some vigour...