The idea of the NHS is to give the whole population access to comprehensive treatment whenever they need it, free at the point of use, so that when you are ill you don’t have to worry about paying a bill.
When and how you receive treatment depends upon your clinical needs, not your ability to pay, as the cost is shared through the tax system.
Many other countries offer a comprehensive range of healthcare but none have such low charges making it amongst the most accessible and fairest in the world.
Through the NHS the risk of ill health is shared across the whole community not borne by the individual.
Gordon Brown once called it “the best insurance policy in the world”. Standard insurance policies always have conditions for paying out, whereas the NHS provides comprehensive care to us all with very few conditions.