This doesn't seem correct:

    The problem is it’s not an easy dataset to get hold of, as it cost a lot of money.
    This is because the data has to be licensed from Royal Mail ...

It seems to be talking about the National Statistics Postcode Lookup UK, which is officially published here: https://www.data.gov.uk/dataset/7ec10db7-c8f4-4a40-8d82-8921...

It's been there from at least 2017, which is when I first came across it.

There are later version of the data set online too: https://open-geography-portalx-ons.hub.arcgis.com/datasets/o...

The license: https://www.ons.gov.uk/methodology/geography/licences

    Under the terms of the Open Government Licence and UK Government Licensing Framework
    (launched 30 September 2010), if you wish to use or re-use ONS material, whether
    commercially or privately, you may do so freely without a specific application for a
    licence, subject to the conditions of the Open Government Licence and the Framework.
    If you are reproducing ONS content you must include a source accreditation to ONS.

If the article is talking about a different postcode address file though, then the above doesn't apply. ;)