More 'recent' information is often difficult to find online. Latest available census is 1911, not all directories online (and those online probably only list business and professional people), etc.
Have you found John in Scotland in 1901 and 1911? (I can't see any likely matches in Ireland but hallmark's link will allow you to search both)
Mother died in 1926 and you believe father might have died c1910. What's mother's status in 1911 census? Have you found them in 1901? (this will help you narrow down a date of death)