The no-nonsense NHS 'guru' Roy Lilley made these two comments a few years ago - they are still a good summary:
"The smart lads' casual conclusion; if our taxes don't pay for our healthcare we will, directly. Left pocket taxes, right pocket insurance. They didn't seem to realise that it's the same pair of trousers"
and
"They could insure but premiums must include an excess for risk, a margin for profit and dividends for the insurer's shareholders. It has to be more efficient for the state to collect taxes and distribute them against a socio-demographic, population based formula? After all, wasn't that the point back in 1948: a disaggregated, mixed economy on the supply-side was costly, unwieldy and impossible to integrate"