Canon Black is in charge of administration in a cathedral somewhere in England, it's never actually stated where. As to his religious obligations, he's rather far away from them most of the time in this series, and that's all I'm prepared to say about him.
You might want to know whether he's a goodie or a baddie. Well I would tell you straight away, but I don't even know the answer myself to that question, and when I asked the author of the series, Andrew Marshall, he didn't know either. So we just have to wait and watch developments.