Ciel Phantomhive's noble title was Earl. In medieval England, an Earl was the same as a Count in other parts of Europe. Phantomhive is his family name; therefore, him being called Earl Phantomhive was understandable. It was like calling Earl Peter Raeves of Wessex "Earl Raeves", or Earl Ian Hunter of Hwicce "Earl Hunter".
My question is, since Phantomhive is his family name and not the name of a region in England (unless in the Kuroshitsuji universe there is a region named Phantomhive, but I've never heard of that), what region/county in England was Ciel the Earl of?