Hi Rosina,
As promised I visited the GRO Office in Werburgh Street in Dublin this afternoon, filled in the form requesting a photocopy of the Marriage Register Entry
Name - Goodfellow, Sarah
Entry Type- Marriage
Year - 1866
Volume - 6
Page - 489,
Registration District - Castleblaney
Handed the clerk the form with the 4 Euro fee and in two minutes I have a photocopy of the full Marriage Register entry in my hand. Success !!!! If you send me contact details by PM I can get it to you .
As to why your request to GRO office in Northern Ireland was unsuccessful I can only speculate. The most obvious answer is as Glensman says, that Castleblaney is in County Monaghan which is in the Republic not in Northern Ireland, so possibly the records are only kept there. However the whole area of historical records is complicated as pre 1922, the whole island of Ireland was administered from Dublin, and the final repositary for all BMD Registers was Dublin. Then after 1922 when 26 counties of Ireland became independent, they continued to be administered from Dublin, but the 6 counties making up Northern Ireland were administered from then on from Belfast. So far so good .... from 1922 all BMD records registered in the Republic are in Dublin, and those in the North are in Belfast .
But what of the Registers from the 1860s up to 1922.?
Well the Index Books to these records contain entries for the whole of Ireland, and are on the shelves in the GRO Building in Werburgh St. in Dublin accessible to visitors for a fee...( these are the index books that the Mormons microfilmed in the 1950s and which form the basis of the BMD records you find on Familysearch ...) And once the Index Entry is found, the GRO clerk only can access the Register pages and produce the requested cert.
So to summarise , I am fairly confident that one can get copy certs for BMDs up to 1922, for any part of Ireland , from Werburgh Street walk in Office or by post from their central Office in Roscommon.( don't ask !) . I just don't know what the situation is for the GRONI . Perhaps someone can clarify it for us.
Cheers
Meath999