This query gives you the coordinates for a given postcode. You must remove or insert spaces in between the outer and inner parts so that the whole string is 7 characters long.
Postcode (must be in 7-character format):
Which database:
Jersey, Guernsey, Isle of Man or Northern Ireland are not covered. (Hoping to add Northern Ireland soonish.)

If you want to lookup postcodes near to a given set of coordinates, you can use my Postcode Reverse Geo Lookup