Additional resources related to my initial question:

Seán contributed a few articles to 'Ceol: A Journal of Irish Music'.
All editions of journal have been digitised by the Irish Traditional Music Archive and made freely available through their website.

Link:
https://www.itma.ie/features/discover/ceol-a-journal-of-irish-music

Seán also contribute some pieces to the Ceol Tíre, the newsletter of the Folk Music Society of Ireland.
These newsletters are also all digitised and freely available online.

Link:
https://folkmusicsocietyofireland.wordpress.com/test-ct-page-2/

*

If anyone else knows of articles in journals written by Seán, or other publications he may have contributed to (printed/online), I would be interested to learn of.

Thanks.
Alan