The NHS is bound to the UK's government economical policies, the main economical policy of the UK since Thatcher is neoliberalism (including Blair's Labour embracing The Third Way of social-democracy); the current Tory government has only been applying those principles ever more. The NHS as a concept is socialist, its implementation depends on taxes which depends on the UK's fiscal policy which in turn is neoliberalist as fuck. Hence the crumbling of NHS as a concept, it is not attainable in a neoliberal economical environment with its business-over-society ideology.
What doesn't make sense is that what keeps UK trained doctors working within the UK?
It's goodwill. They could improve their lives immensely with a move to Australia, and New Zealand. If they are willing to do another round of exams on par with their finals they can go to Canada and the US.
That's what it means when I say it's staffed by goodwill.