People can do whatever they want in the UK when it comes to healthcare - you can go to the NHS or go private if you want. Nobody makes you go to an NHS hospital.
Of course, what you can't opt out of is the tax bill that pays for the NHS - but as the NHS is reasonably efficient I don't mind paying for it if it means that everyone in the country has access to decent health care.
Of course, people might not be able to do everything they want without socialized medicine, whether it's because they can't afford the risk, privatized medicine costs too much, etc. A liberty principle doesn't cut evenly one way or the other on this issue.
