You'd be right in thinking that ethics and socially sensitive research are separate. In the exam, you can put SSR into an ethics essay, but you can only get away with putting ethics into a SSR essay if the issues are relevant (for example, confidentiality is paramount in senstive areas, where divulging information may lead to divisive social policies - e.g. findings from AIDS research may be used to back compulsory antibody testing). A popular question seems to be "discuss the ethics of socially sensitive research". In this case, you need to be selective, and pick a few ethical issues that are pertinent to topics such as race and intelligence, genetics etc. I'm sitting the unit 5 exam in summer also so if you email me your essay i'll have a look at it if u would like some feedpack on it.