Doing a general Google search for John Curwen Pottinger I came across the Borough of Richmond upon Thames website. They have a search facility for all entries in their burial registers. Hooray John Curwen was there and the results gave me the date & place of burial, age, last place of residence and the plot references.
Richmond also have a scheme whereby you can volunteer to look after a grave. The council do the general maintenance of the cemeteries, but don’t have the finances to weed each grave. So they ask that anyone who visits regularly or who lives nearby considers adopting a grave and look after it. Sounds like a great scheme and one that I am sure that genealogists might well like to become involved in. Wonder if you get to chose which grave you look after, personally I would chose one which had a headstone with plenty of genealogical details on it!!