Hi Helen-
I have been researching my Irish ancestors for a few years now - I have to say it is very "challenging". One suggestion I have which may dovetail with greenpaula's suggestion. Were William Scully & Paula Cope still alive & enumerated on the 1911 census? I struggled for many years with my 2x great-grandmother, Margaret. I knew the family was from Co. Derry in Northern Ireland - but try as I might I could find no information for Margaret in the Parish registers, nor any marriage entry. ( I was lucky enough to know the town where my 2x great-grandfather & great-grandfather were from). I assumed Margaret was from the same place. After the death of her husband she moved to England and lived with her son. On the release of the 1911 Census - it had recorded the following information about her: how many years she had been married, number of children she had had (6, I only knew about 3 of them) and her County of birth - County Tyrone! I now have a better idea of which years to concentrate on to look for a marriage cert. and
am at least I am a step closer to narrowing down a parish in order to try and track down her marriage to John, then perhaps proceed and try and ascertain where she was born. I am ever hopeful!!
Personally, I would start by trying to establish their religion, and then ascertain whether you will be looking for the couple in the Republic or in N.I. The suggested Surname search should be very helpful in that area. Try this website for a surname search
http://www.irishtimes.com/ancestor/index.htmIt may be of help.
I know it really is tricky, its almost like looking for a needle in a haystack.
All the best
[You may not have found them on the 1861 Census as they may have travelled to Sunderland via Scotland, many did! ]