Google (well, Startpage actually) is still your friend. Just one of many, incidentally from the same sources used to refute the point. See here: Keogh review into 14 NHS hospitals did not find disaster on scale of Mid Staffs | Society | theguardian.com
Presented are some very credible reasons, both to be vigilant and to be skeptical. We are too quick to hop on the train to blame a system rather than ensuring that the data is apples to apples, and that it's not being misinterpreted (and not necessarily with any agenda, statistics once again are tricky and malleable.) Our system is broken, their's may be damaged, both are fixable and neither alone are the answer.
Also, it isn't raw data. It has been reduced and analyzed and had recommendations made based on its veracity. The raw data needs to be looked at through other filters, it is amazingly easy to unintentionally skew data in any of the steps and bears further scrutiny.
Just like our "global warming" debates. the initial knee jerk to the statistical models didn't grab all of us up. When we questioned it aloud we were shouted down. Just now are other scientists looking at arguments that we presented a decade ago that influence the interpretation of the data, in ways that are yielding results that do not support the forgone theoretical conclusion of man-made climate change.
I don't believe the OP was "on the train to blame a system". The OP was pointing out the current state of health care in England which has had 60 years to get single payor socialized medicine "right". We can look down the road and see where we in the USA will be.
The source(s) don't matter. The truth is the NHS has a real problem with excess mortality based on the Keogh review which was ordered and performed at the behest of Parliament (like our OIG).
In addition to mortality, imagine the thousands of patients waiting in an ambulance in the parkiing lot of the ER for hours and hours because the ER won't let the ambulance unload! Now that would be something in your local ER!
2008 Scandal of patients left for hours outside A&E | Society | The Observer
2013 Patients facing eight-hour waits in ambulances outside A&E departments - Telegraph
Lots of improvement in 5 years, say whot?