Yup. You are probably right. Impossible to provide bus services to hospitals due to deregulated bus service.
Meanwhile in Cornwall which you cite:-
http://www.royalcornwallhospitalstrust.nhs.uk/DocumentsLibrary/RoyalCornwallHospitalsTrust/Websites/Internet/PatientsAndVisitors/GettingHere/BusRoutes.PDF
where surprisingly I've used BOTH trains and buses even on a Sunday! (You getting confused with the Isle of Lewis and the Wee Frees?)
Thinking about it all a bit further, perhaps the hospitals could subsidise the bus services by selling off the cars of patients who drive to the hospital but die while they are there? There must be a good few over the year one would think.