No, you don’t have to have Private Health Insurance to go to a private hospital. There are a number of hospitals that allow you to self-fund treatment.
However, this can be an expensive option. A surgical procedure such as a hip or knee replacement can cost more than £10,000 just for the procedure, without any additional costs associated, such as x-rays, scans and outpatient followup appointments.
So, while self-funding private healthcare is possible, it’s only really an option for wealthier people. Private Health Insurance, on the other hand, spreads this cost out into what could be more affordable monthly payments.