It doesn't. It provides - as resources permit - healthcare free at the point of delivery for those who wish to avail themselves of it. Privately-funded - either directly or via insurance - is not illegal in this country, so it is incorrect to say that the government controls access to healthcare.thanks for confirming why the government does not need to control health care.
A further point: in what way is an NHS hospital trust manager making decisions about which treatments s/he is able and willing to fund any different from a private healthcare insurance company making the same sort of decisions based on the same sort of criteria? Whether the healthcare is publicly or insurance-based funded, the same hard choices need to be made from time to time.