Latitude gives you a position in terms of North/South, i.e. up and down the globe. It is zero at the equator, positive in the northern hemisphere, and negative in the southern hemisphere.

Longitude gives you a position in terms of West/ East, or left and right of a particular point on the globe. That point is called the prime meridian and is located at Greenwich, just outside London. There longitude is zero. To the right, i.e. east, longitude is positive while to the left, i.e. west, it is negative.

The approximate latitude and longitude for St Agnes are:

latitude 50,320
longitude -5,200.

More specifically, where Vicarage Rd meets Town Hill they are:

latitude 50,312
longitude -5,204.

While at Trevaunance Cove they are:

latitude 50,320
longitude -5,206.