Hi
I have used Deceased Online a good many times over the years.
They have good coverage of the Greater London area and I have seen A LOT of grave plots with a lot of almost always unrelated people buried in them. In a populous area like London, I guess it's hardly surprising.
On the burial scans you can sometimes see the depth at which someone was buried annotated (in my cases) on the right hand side. So, if you check "others in grave" you might work out who went in first by the date and who's on top of who by the depth buried.
Of course, there were double plot or family graves which would have been purchased outright. Although, that didn't always work out the way planned...I've seen grandparents with grandchild, a husband and his neighbour and some plain odd combinations. Perhaps people forgot to tell their heirs where they had bought their space of eternal peace.....these days 25 years top whack!
On that note....Season's Greetings!
Rebel