If you wait until you hold an offer before starting the vacc course, you may not have documentary evidence of immunity to give to the uni before enrolling. Some medical schools have been known to withdraw offers at the last minute because people haven't been vaccinated in time. Also, some people don't get offers til Clearing in August, and at any rate most people's offers aren't confirmed until A Level results day, at which point its a tad late to be starting your jabs.
The point about the cost of the jabs to the GP I got straight from the horses mouth; I work at a GP surgery and the partners said the cost wouldn't be renumerated by the PCT. My own GP surgery said the same.
The 'employer' has done all they can to ensure your H&S; they provide information and make it quite clear that you need to get yourself vaccinated before you start medical school. It's then your own responsibility to make sure you do that. The change in the way medical courses run has meant that instead of not meeting patients until clinical years, you're coming into contact with them from Week 1, so immunisation from the moment you set foot on campus is imperative.
How can there be areas with high demand for immunisation? Areas with significantly more healthcare workers?? I'm personally not aware of Hep B immunisation being provided for any other reason; I realise IVDU's are a high risk group, but it's a bit tricky getting them to attend for three separate jabs months apart, so AFAIK they aren't vaccinated.
Just don't go down the route of 'I've paid my taxes, therefore I'm entitled to everything on the NHS'. The NHS is free at the point of entry, or whatever the official line is. It provides fantastic healthcare, but if you want additional things, such as vaccinations not considered to be essential, extra scans during pregnancy, or a hospital more like a hotel, then you have to pay. I think that's perfectly fair.