I love looking at old grave stones! I know where Dulwich is, but never have reason to go there unfortunately. You might be lucky though, I have a feeling there are a couple of MNer who are closer than me.
Could they be buried in West Norwood or Nunhead cemeteries (both very 'fashionable' places to be buried at the time)? I think you can find information about WN cemetery from the Lambeth archives and guess Southwark has something similar for Nunhead.
If you go to some municaple cemetries in London - or just on the outskirts as they were when they were built. Sometimes if you visit in the week the office will be open - ask there if you are allowed to search for a particular name in the register, it will also give the location of the grave.
Otherwise it may take two to three days to find the location of the grave and you may need camping equipment for the trip
Hi Wallace, I went to the graveyard today and had a look for your monument but I didn't take the details and could only remember the name so I didn't find it. It is a HUGE graveyard and very beautiful, this morning was a glorious morning and I really enjoyed the peace and calm (hope that doesn't make me weird!). It's hard to find solitude in innercity London but I did today, I didn't see another person and I was there for an hour. I will write down the details and try again next weekend.