Thanks, Jim,
Yes to your Q about Wikipedia, a reference in the article refers to official biography produced by HoP staff, and there are multiple newspaper references (on FindmyPast) to said MP attending weddings, soires, and Bank meetings (he was a director of a Dublin bank) - but none mention that person as RGH.
I will explore your suggested alternatives, the "suggested date" for my GF's father RGH was speculative as GF was born in 1856 ( so RGH could have been 20-30's when GF born but your suggestions equally possible).
Elsewhere in G2G I have noted a 1921 Census transcription for my GF giving his birth-place as "Dublin" (like other sources) but this one attributed it to a tiny hamlet (in or near Suffolk). None of the other sources explicitly say "Dublin, Ireland" as one would assume the city was meant. Either way intriguing cracks in a long-standing brick-wall, Thanks for your help.
Phil p.