Postcodes are a lousy navigation mechanism in rural areas. Even if your navi has been updated recently. And even Feral’s mate who provides the server for this site only updates his GB postcode database every 3-6 months when a new version of CodePoint Open comes out.
What you should have done, you peasant, is give a latitude and longitude like a grown-up. Lat and long works on every navi, and on paper maps too.
(Mapcode is very nifty but hardly anything uses it.)