Thanks for your comment Macwonga.
The coordinates for this site were taken from the raw data downloaded from the NPI website as the address given wasn't enough to geocode with Google Maps. It seems the position is out by around 7km. See the NPI version of the map.

If there is sufficient interest I'd be happy to provide an update with corrected coordinates, but I'm not able to check every site myself. I hope you'll agree that importing the data into Google Earth is an improvement.