You need to know your latitude before you order your Spot-on Sundial - the angle of the gnomon (which casts the shadow) has to be the right one for your location.
You also need to know your longitude later on when you come to set up your Spot-on Sundial, so it is worth writing it down for later.
www.latlong.net Click on the map and the latitude and longitude of where you've clicked will be shown. Alternatively click the 'Get Map Centre' button to get the location of the centre of the map. Or you can type the latitude/longitude to see the location on the map. And you can use Street View to improve your positioning, where it's available.
www.mapcoordinates.net Type an address into the search field in the map. Zoom in to get a more detailed view. Move the marker to the exact position. The pop-up window now contains the coordinates for the place. Just copy the values for longitude and latitude.
Or you can using google maps, with instructions provided in the support page attached here. www.support.google.com/maps