It is my belief that as long as your vehicle carries a current Road Fund Licence (tax disc, or whatever) proudly displayed in the prescribed manner, then you should be able to park wherever you damn well like!
Furthermore, if you have legitimate business on hospital premises (and why else would anybody be there?), as a British tax-payer or entitled overseas visitor, you should be able to park free of charge at the hospital you are visiting.
Any deviation from this should be challenged in the courts!
Please note, that other service providers (eg, the much maligned Tesco et al), welcome customers by permitting free parking. But note also that (in my experience), NHS car-parks are irregularly “policed” and many have only one wheel-clamp!
