"this isnt a necessary life saving surgery as such the doctor has every right to decide which patients he will or will not take."Physicians are subject to various constraints on their freedom to accept or reject patients.
For starters, they are subject to the same constraints as any other provider of services to the public, where there is anti-discrimination legislation in place. Presumably, they could not legally refuse to treat someone because of his/her race, religion or sex, for instance.
They are also subject to professional ethics requirements that are administered and enforced by professional governing bodies. Up here, we commonly call them "colleges", e.g. the "Ontario College of Physicians and Surgeons"; I think that down there you tend to call them "licensing boards". Essentially, governance of the profession is handled by the profession itself: "self-governing profession".
On the first point, refusing to provide services to a person who is HIV positive might be unlawful discrimination under local law. It likely would be here, since being HIV-positive is regarded as a "handicap" (in the rather archaic language of the Ontario Human Rights Code) and is therefore, as the Human Rights Commission interprets that legislation, a prohibited ground of discrimination:
http://www.ohrc.on.ca/english/publications/hiv-aids-policy.shtml-- and in fact the Commission has a policy of expediting complaints filed by persons who self-identify as HIV-positive. (That policy statement is well worth reading, for anyone with a deeper interest in the issues.)
On the second point, professionals like doctors, lawyers, pharmacists, engineers and architects are given privileges by society, and have duties in return.
They have the privilege of having the exclusive legal authority to do certain things in return for payment: perform surgery, represent clients in court, dispense drugs, design certain structures. When the profession limits admission to the practice of the profession, as they all do, its members benefit financially, in particular. If we could all perform surgery, it would be a lot cheaper, and doctors would be driving smaller cars.
A refusal to treat an HIV-positive patient might well be regarded as a breach of medical ethics, one common basic tenet of which is that the patient's interests are paramount in almost all situations.
But hell, if pharmacists are to be permitted to refuse to dispense hormonal contraception to women, when the only risk they are taking is the risk of falling down in their duty to oppress women ...