Ordnance Survey "OS OpenData", at https://www.ordnancesurvey.co.uk/opendatadownload/products.html Product Code-Point® Open > du -b codepo_gb.zip 15504173 codepo_gb.zip Contains coordinates in OSGB36 format: "SO515RU",10,"X",-99, -99,-99,-99,-99,-99,-99,437015,120914,064,"Y06","QD3","24","UN","FW","X" ^ postcode ^ easting ^ country code ^ administrative county code ^ positional quality ^northing ^ NHS regional health authority code ^ NHS health authority code ^ administrative district code ^ administrative ward code Use Geo::Coordinates::OSGB to convert the eastings/northings to lat/long: > perl -MGeo::Coordinates::OSGB -E'say join(" ", Geo::Coordinates::OSGB::grid_to_ll(260525,664816));' 55.8563597114678 -4.22849648841559