I don't expect anyone to be able to answer this, but hope to be proved wrong. Does anyone know if there is a reasonably comprehensive source of old postcode data? I have data going back a few years and a fair proportion are codes that appear to have been been retired by Royal Mail. Has anyone has found decent source of such codes?
This site UK Data Service has historical postcodes from 1988. But I don't know if it is open data since I have to login. I hope this will help you :)
Postcode data is now available on the ONS website.
From that page you can download a CSV file which when uncompressed is over one gigabyte in size. One of the fields is
DOTERM, which gives you the date of termination. It therefore should be a comprehensive source of data on retired postcodes.