Is this my 3 times great grandfather?

I have found a record of a "Denis Hannon" in the Griffith's Valuation for the townland of Ballagh in the Paris of Rahara.

I am trying to find out more information about him to see if he is, in fact, my 3 times great grandfather.

The little information I have about my 3 times great grandfather has been gleaned from researching the history of his son, John (my 2 times great grandfather), from UK sources. From my researches I know that:

my 3 times great grandfather, Denis, was a farmer and had died prior to John getting married in a Roman Catholic Church in Huddersfield on 8 February, 1858

and that:

John was born in Roscommon, Ireland in, I believe, 1824 or 1825

I have found no evidence of Denis in England, and my earliest evidence of John in England is in the 1851 census, where his surname appears with the alternative spelling "HannAn".

I hope someone can help. Ideally, I should like evidence establishing the relationship of father to son, but even evidence of NO relationship, will enable me to start looking elsewhere! 

Thank you in advance for any help you can give.