Some cemeteries in London reuse graves after just 75 years
https://en.wikipedia.org/wiki/City_of_London_Cemetery_and_Cr...
I have very vivid memories as a child of walking through Brookwood Cemetary in south east England seeing a big machine crunching up headstones. Vast swathes of the place was flattened. The cheat code here seems to be "topple testing" for health and safety reasons.
It's the UKs largest cemetery and in a shocking state: