Enter eastings and northings as per the British Ordnance Survey National Grid in the complete all-numeric format down to 1 metre precision i.e. 6 digits each (northings in Shetlands and Orkney Islands can be 7-digit).
OS Grid Eastings:
OS Grid Northings:    
alternatively you can enter latitude and longitude in WGS84 system (=the one used by GPS)
N latitude decimal degrees:
E longitude decimal degrees (use negative for W longitude):
How many postcodes (default=20):
with map: (tick if yes) satellite: (tick for satellite, leave unticked for roadmap) zoom: (default=16, max=21; zoom+1 = twice as big map)
Which island: Great Britain Northern Ireland
Jersey, Guernsey or Isle of Man are not covered. (Northern Ireland being added--experimental!)

If you want to lookup coordinates of a given postcode, you can use my Postcode Geo Lookup