I too have found the parish office people very helpful. The one man I spoke to even offered to meet me at St. Michaels to take us to the grave location because they had no markers.
I also have numerous people buried there as per the City Death's but the parish has no record of them. Apparently many of the early records were destroyed in a fire--sometime around 1900. I know I have one buried in 1904 which there is no record. I also believe they have the records for St. Peters.