HI There, No problem. Now I would suggest that when you contact Rothe House ,Parliament Street, Kilkennyyou give them as much details as you can.
They will be able to help you much better than I, as they have access to alot of records . seeing that your grandfather was in the Royal Fusiliers there has always been a military Barracks in Kilkenny and one in castlecomer. also I think the reason for the child being baptised in Mothel could be that Rebecca came home to kilkenny for the birth of her child and Mothel may have been her parish church.Also could william have been stationed in Kilkenny at the time?? well a search through the church records may help as far as I know Rothe house keep copies of church records both catholic & protestant churches. And inMothel thereisa Church of Ireland Church & a catholic one.
Hope this helps.
Regards,
Summerhill