Generally. you see a GP (general Practitioner).
GP can order prescription to do blood tests, prescription for ordinary medicine.
GP cannot treat Hepatitis B. will refer you to a Hepatitis B specialist (N.B. usually long waiting time for appointment).
GP fee, HBV specialist fee, and blood tests are all expensive for non-citizens.
Please check whether your visa requires compulsory Health Insurance (usually existing conditions are not covered, HBV medicine also not covered.)