... Robert DOWNEY & Rose Ellen BURNS are my maternal great-great grandparents. Their son Robert Jnr is my great grandfather. He married Susan LONG at Dromore RC Church, she died in childbirth, and his 2nd wife was a protestant girl Gertrude Annie FAULKNER from Desertlyn, Londonderry where they married circa 1885 and we assume this is when he gave up his catholic faith ..
May be having a senior moment, but the only marriage I can see of a Robert Downey to Susan Long in the relevant timeframe took place in 1877 in County Leitrim, some considerable distance from the geographic context to this point of Dromore County Down. There is a Leitrim townland in County Down, but the Robert Downey / Susan Long marriage definitely took place many miles away in County Leitrim.
I'm also struggling to find a civil marriage record on GRONI online for Robert Downey and Gertrude Annie Faulkner, do you have any further information?