I copied and pasted the lyrics without proofreading them
Correction highlighted in bold:
We remember as long as the bright red poppies grow

To me it sounds like Alex Allen sings "the 19th of July", even though the youtube video gives the words as "the 9th day of July".
I looked up these dates for 1916. 9 July was the date of the Battle of Verdun. The Attack at Fromelles took place 19–20 July 1916. And how long would it take for a mother to actually hear of her son's death?

All the recordings I sampled use the same tune as the song Working Man (It's a Working Man I am and I've been down under ground...)

Although in Northern Ireland, the Battle of the Somme is mostly commemorated in the Unionist/Loyalist community, there were plenty of Catholics - even some who were strongly Nationalist - from Ireland who served in British troops in WW1. There were also women who served as nurses and doctors.
https://www.irishtimes.com/culture/heritage/forgotten-heroines-the-irish-women-who-died-in-the-first-world-war-1.3690961

Medical doctor Elizabeth Gould Bell, who survived the war, but lost a son: https://en.wikipedia.org/wiki/Elizabeth_Gould_Bell