Where I used to live you generally had to pay for an ambulance (in case of abuse) and that was about 300 GBP (if you wasn't insured) and about 600 GBP if a doctor was involved so everything would be cheaper than calling for an ambulance. People always hesitated and made sure it was absolutely necessary because if not you were automatically charged but as long as it is for free where is the point in calling a taxi? (That's my opinion - sad but true and that is NOT a complain about your "fantastic" NHS in this country or something like that)