How to find the latitude and longitude
If you have one of them new-fangled GPS devices or a location finding app on your smartphone, getting the latitude and longitude should be easy – you just have to remember to note it when you're actually at the bench!
Otherwise you can use Bing Maps or Google Maps to give you the latitude and longitude.
Bing Maps (unlike Google Maps) will let you see an Ordnance Survey map which may be easier to use.
Hover over 'Road' at the top left of the map and select Ordance Survey from the drop down menu. See the screenshot below. (You may need to zoom in on the map before the Ordnance Survey view appears.)
You may be able to actually see your bench using the satellite or bird's eye views. These views can be selected from the same drop down menu as the Ordnance Survey view.
Right click on the map at the spot where your bench is and a menu should appear. At the bottom of this menu there is the word 'copy'. Click on this. See screenshot below.
The longitude and latitude will be copied. You can now paste this into the 'Latitude and longitude' box on the 'Add a bench' page. Job done.