The latter proved to be an epic sleuthing exercise with 3 men of the same name in the regiment at the same time and after much painstaking cross-referencing of the original ledger entries with their small, faded, spidery writing, I think I worked out which one of them was at least in Scotland when his son was conceived!
The story must have amused the Editor as I was lucky enough to be awarded Star Letter for the month and I am eagerly awaiting the delivery of my prize of an Ancestry DNA test. I will need to swot up on how to make best use of this new research tool for me, but honestly, nothing beats going back to the original documents and recreating the stories. Those same ledgers went to war too in the wagon train to Waterloo or in the saddle bags to the Crimea and you can lay your (gloved) hands on them and touch history. Make the time to do this sort of research and I'm sure you will be rewarded too.
From an Irish research perspective, don't forget that the British army recruited thousands of Irishmen, eager for better food and better pay. The East India Company Armies were also home to many Irish emigrants and you will find their muster rolls and other related documents in the British Library India Office and some selected resources online with FindMyPast and FamilySearch. See my web page "Fighting in a Foreign Field" for more advice and links.