For best results enter only your complete postcode e.g. SW1A 1AA
We have data for postcodes, and good approximations for postcode districts (the bit before the space, e.g. SW1A). Thank you to the Ordinance Survey for finally seeing sense and releasing this data.
To find other addresses we use either the Yahoo or Google geocoding services, which you can select via the dropdown. For best results enter as much of an address as possible. Yahoo seems to be more accurate, but they both have their foibles.