Under Key findings:
Its main weakness is health care outcomes. The UK appears to perform less well than similar countries on the overall rate at which people die when successful medical care could have saved their lives.
Among its strengths, the NHS does better than health systems in comparable countries at protecting people from heavy financial costs when they are ill. People in the UK are also less likely than in other countries to be put off from seeking medical help due to costs.
So: main strength - cheap, main weakness - health care outcomes!
It's no surprise that fewer people in the UK skip medical care due to costs when it's (close to) free. The problem is that the health care is bad when you get it (according to your own provided document)!