I'm displaying a map of territories, which consist of UK postcode districts (e.g. SN12)
The wikipedia page for each postal area includes a kml file that includes each district separately, which I'm using to combine and plot on my map.
My issue is that there isn't one for the BT postal area, there's only a SVG image.
Where can I find a KML file like the ones that exist on wikipedia for postal areas, but for the BT area?
Tabular data about post code data is at MySociety.org:
ONS Postcode Directory (ONSPD), February 2012 edition (thanks dvdoug!). This include full UK (including Northern Ireland) postcode locations.
Those files don't include the headers, which is annoying. This page has a version from a different vintage which had a header added. If it's 47 columns, hopefully they match, but it's taking an age for me to download.
It looks like Northern Ireland has some more complicated licensing rules for commercial use, which may have contributed to that data being harder to find when the Wikipedia pages you're looking at were originally created.
It looks like someone has approximated shapes for the BT postcodes which you can see on this Open Street Map page. Getting those in a useable format is pretty obtuse, as best I can tell.
To conclude, I'm sorry that the original text of this answer was misleading: the source I identified doesn't actually have what you need. You may have to contact NISRA; maybe more requests from the public will chip away at their data publishing process.
There isn't one currently available as open data. As Joe noted, NISRA has its own licence.
If you just need the whole BT area as one polygon, Doogal's postcode districts has it. All the 2008 BT district postcodes are available as KML points, but you'd have to do some analysis to approximate the areas. The folks on Geographic Information Systems Stack Exchange could help with that.
Alternatively, if the licensing from UK postcode districts - Google Fusion Tables is acceptable, you can filter this table for just BT postcodes and output that as KML. (link source: location - How did google get the outline for postcodes on maps? - Stack Overflow)
The Ordnance Survey recently released a new API and you should be able to get administrative boundary data, including post code boundaries: http://www.ordnancesurvey.co.uk/business-and-government/help-and-support/web-services/code-playground.html
