Nellie, found your Robert Hughes on the Ulster Covenant web-site with the address as Olive Terrace as mentioned in your other posting. You say they attended Strand road Presbyterian Church,i wondered what you based this information on. The reason i ask is Robert signed the covenant at Glendermott Presbyterian church which is some way from Olive Terrace [but so is Strand road] and i wondered if they had started attending another church as there were closer sites to Spencer Road/Olive Tce to sign. If so there are two or three graveyards in the vacinity of Glendermott. In addition as other replies have stated they may have been buried further from the City,perhaps where they originally came from. Do you have the 1901/1911 census for them as it may give details of their place of birth.
My Great-grand Father was John Young McConnell [Young was his Mothers Maiden name]. His wife[nee Cowan] was buried in Leckpatrick burial ground which is in County Tyrone but close to where she was born,although they had lived in Londonderry for at least 30 Years.
Rob