Thanks but I don't think my curiosity extends that far at the moment. I have been in contact with a relative of these people so if it turns out to be of interest to her we might take it further in the future.
The plot number puts the grave in EE1 so the EE entries are incorrect, my guess is a clerical error.
My theory was that maybe a pathway was added after 1931 but the child burial in 1906 scuppers that idea as it was entered as section EE1 (I have checked the entry in the burial book) This is a purchased plot but I don't have any record of a memorial.