Sorry, no luck with any of the dead on your other post.
The only Oliver grave I have, just in case they're yours, is for:-
Joseph Oliver d 27-May-1879 a 60 (husband) d reg Mile End
Ann Oliver d 9-Jul-1883 a 57 (wife) d reg Mile End
Alice Oliver d 19-Mar-1893 a 33 (daughter) d reg Kensington (says age 32)
Looking through my photos, I'm afraid I didn't find any clues which would help your search. There are a few 1860s graves scattered around, but I didn't come across any solid area at that era. I came across one area off the path strewn with the miniature gravestones typical of common graves, but from the WW1 area onwards. As is frequently the case when these stones have been disturbed by growth of vegetation, they were scattered around randomly. If, as seems likely, the accident victims are in common graves, I advise taking a list with every name in every possible grave, as only a few people in such graves got headstones.
Very few gravestones I saw had numbers, and an FoTHC page says graves are rarely consecutively placed, so I don't think the number will help unless FoTHC have a plot map. Though I have seen other people mention prefix letters, the numbers I found on stones didn't have them; the cemetery plan on the gate divides the cemetery into a grid of numbered squares.
Sorry I can't be of any more help.
Chris