some s_exton's (spelling to avoid naughty word!) records are held by Manx Museum - these usually tell you where the bodies were. The burial act of 1867(or thereabouts) required all yards to employ such a person - the records should be with the parish or in the case of towns the local authority for yards that are still open for new burials.

There should be other records of who paid for a grave to be opened or in case of a family plot who bought the plot.