If you need to get geographic co-ordinates for a postcode you can use the Ordinace Survey OpenSpaces web api.
First sign up for a developer’s key here.
They will email you a key which you can use in your javascript to access the service. Here’s a snippet of code which will get the co-ordinates for a postcode. The co-ordinates will be in BNG (British National Grid) co-ordinate system, which gives you a easting and northing co-ordinate. These figures represent where the location is on a grid overlaid over Britain (ranging from 0, 0 to 1300000, 800000). You’ll need to substitute your api key for the text ‘YOUR_KEY’.
<script type="text/javascript" src="http://openspace.ordnancesurveyite.co.uk/osmapapi/openspace.js?key=YOUR_KEY"></script>
<script type="text/javascript">
var postcode = "BS8 1UB";
var pc = new OpenSpace.Postcode();
var callback_func = function (data) {
var easting = data.getEasting();
var northing = data.getNorthing();
console.log("Here is the data:");
console.log(data);
console.log("Easting: " + easting);
console.log("Northing: " + northing);
};
pc.getLonLat(postcode, callback_func);
</script>