I don't want to rain on your parade, but don't get your hopes up too high
Even if the records show that your ancestors were buried in a particular churchyard or cemetary, there's no guarantee that you'll find a marker for the grave.
There's lots of pitfalls.....
- Your ancestors might not have been able to afford a stone. Sometimes (especially in the country areas) people opted for simple wooden crosses with brass plaques, and these didn't survive much more than 70 years.
- Your ancestors may have had a gravestone, but stones over 100 years old may not be readable, especially in London, where pollution was a lot higher.
- Your ancestors may be buried in a communal grave, which may or may not contain the remains of other family members. You will at least know where their resting place is, even though there probably won't be a stone with their name on it.
But there can be positive things, too. Recently I was able to track down where by g.g. grandparents were buried, and the church archivist showed me the area where the gravestones were (the burials were in the 1860's). Unfortunately, the stones had been demolished in one of the storms that we had in the 1990's, when a tree fell on them. However, the archivist also told me that one of their grand-children was also buried in their grave at the age of 4 (although they never knew her), so at least we knew the resting place of the poor mite. The archivist also gave me details of who was buried in the same plot as some other of my ancestors, which has helped me piece together the relationships of other people in the area with the same surname.
I hope it all works out well for you