I may be wrong, but as far as I know the only way Edna and Stanley would have a 'plot' at Anfield is if their cremated remains were actually buried in a grave within the cemetery (possibly in a grave of a family member who had a burial rather than a cremation).
Burial of cremated remains was required to be recorded in the burial registers and also the in the grave registers. I doubt the cemeteries dept would be able to help with section/plot numbers as it appears that there is no record of a burial of ashes taking place for either of them.
I looked for an example for you to explain what I'd expect to see
A Thomas Blundell . who had died age 76 was cremated at Anfield 10 Dec. 1990. I know you have access to Ancestry, this is a link to his entry in the Register of Cremation
https://www.ancestry.co.uk/imageviewer/collections/9041/images/49092_557030-00359?and then his family must have chosen to have his cremated remains interred in Anfield Cemetery and that happened on 20 Dec and was duly recorded in the Register of Burials at Anfield Cemetery
https://www.ancestry.co.uk/imageviewer/collections/9041/images/48242_557055-00316?Both events, cremation and burial of ashes, recorded correctly as expected (and required by the cemeteries)
Boo