Hello Dorothy
You can search for details of Manchester burials at
http://www.burialrecords.manchester.gov.uk/ - the index is free, but you have to purchase credits to see more details.
According to the free index, Irene Miriam Lucas was buried in Southern Cemetery on 11 January 2008 in the same grave as her husband: no one else was buried in this grave.
Irene's mother's maiden name was Riste, and an Elizabeth Riste married Samuel Ditchfield in 1916. (FreeBMD) The most likely birth I can see is in Chorlton district in 1890, and an Elizabeth Ditchfield of the right age died in 1979 and was buried in Southern Cemetery on 7 November 1979 in the same grave as Samuel Ditchfield and Mary Elizabeth Williams - does that sound right?
I can see a Linda Rose Lucas buried on 25 January 1980 in the same grave as Darren (aka Darren Moore) Lucas, who was buried on 16 August 1978: there are some other members of the Lucas family in this grave.
I hope this helps.
Rambler