Interesting how locations change protocols about, yes? Here in the States the letter would be usually be addressed to hospital administration (either the administrator themselves, or a patient liaison), who oversee both the medical staff (doctors, nurses, techs) & non-medical staff, or to the chief/attending (doctor) of that department, regardless of whether it’s a doctor, nurse, or support staff issue. Although it can vary a lot, hospital by hospital. In some it’s the social work department who interfaces with patients/family, in others all complaints are directed to the the legal department, the dean of medicine, or director of nursing. So we always have to call to find out who is the person/department who handles patient care issues.