* The Ordnance Survey National Grid Reference (and corresponding Latitude/Longitude) given at the top of the pages describing individual sites usually refer to the location of the closest or most prominent entrance to the site where the monument is to be found - e.g. a gate into a churchyard. For monuments located in open country, or at a significant distance from the site entrance as just defined, the co-ordinates usually refer to the exact location of the monument.
Please allow for a small error in the co-ordinates of up to a couple of dozen metres.

Thanks to the people at streetmap.co.uk, if you click on the Grid References in the magenta boxes on the site pages, 
you'll see an extract from the relevant Ordnance Survey 1:50000 Landranger map!

As the official mapping agency of the United Kingdom Government, the Ordnance Survey produces the definitive maps of the country. They contain a wealth of information.
 For more details, visit www,ordnancesurvey.co.uk/leisure