Converting from PostCode to map reference is far from accurate, but it can be done using the Google Maps API. You can get a Google Maps API key from Google by just asking for it, although you are limited to a certain number of requests each day.

Google Maps usually works through JavaScript, but it is possible to ask Google to return the data in JSON format and then use the PHP function json_decode() to decode the information into a usable array format. To get Google to return the data in JSON you must pass the parameter "output=json" in your query string.