Free for the first 15 minutes, then 1.20 an hour, with £12 maximum charge. There are concessions, e.g. discounts if you are attending a course of treatment for 3 or more days in a week. Also free parking for resident parents of children in hospital, or babies in NICU, for relatives of critically ill or end of life patients, for blood donors.
There is also a weekly rate, which is heavily discounted. I wish I'd known about this when my DD was in for five days after her C-section - I spent most of every day with her and my DH came in separately for an hour or so each day. We clocked up a fortune in parking fees!!
Yes, there is a problem with people using the car park for free and going off elsewhere - the hospital may be a good walk from the town but it is on a bus route (as most hospitals are) and would serve as a very handy free park and ride service!