Freddie's medical records would have been destroyed ten years after his death, possibly even before then. There was no inquest and no reason to doubt what happened with him. His GP was private, so they wouldn't even be on file with the NHS, and they wouldn't be on file by now anyway even if they were.
I can't really imagine that they'd make for interesting reading. Peter Freestone and Jim Hutton both shared quite a lot of very private information on Freddie's condition. I'd go as far as to say they shared too much, actually, but obviously there's a need in people to know this stuff..... (hence this thread). Buying Jim's book and Peter's book on Freddie will tell you as much as you need to know. You could also google AIDS or watch documentaries about the early days of AIDS if you want to know more.
Otherwise just enjoy the music, it doesn't do you good to fill yourself up with too much negativity, and I don't think Freddie would particularly want us obsessing over this.
miraclesteinway