Historic counties are an approximation only, and do not take account of "detached" parts of counties or counties corporate.
For Category C Listed Buildings you will need to drill down further into locality, as there are too many to display on a single county map.
Where possible, locality names are civil parishes or civil communities. Where there are no civil parishes, such as larger towns, cities and boroughs or unparished rural areas, the locality name is the relevent district, borough or unitary authority ward.