I've posted about this before but it bears repeating - THE NHS IS THERE FOR THOSE WHO NEED IT!
It is not there for those who deserve it, it is not there only for those who have lived wholesome lives and never made a mistake and never done anything to jeopardise their health. If it were, NONE of us would get free treatment!
If you start punishing people for mistakes by charging them for treatment, you are bringing into question people who have cancer (did they smoke, did they sunbathe, did they eat unhealthy food?), people who have heart disease, people who have muscle and joint problems, people who have infections, I could go on and on and on.
Basically whatever your opinion is on abortions, this argument is a very slippery slope and goes against the principles on which the NHS was founded.