In summarizing the notes above, it would seem that John and Catherine Robina Lyall are buried in Andreas parish.
As David said, there is a map of the several graveyards at the beginning of the MI books by IOMFHS. These note the grave #s not the names.
I have the MI books for Andreas Old Yard, East-West Yard and St Jude's and there are NO MI's for any Lyalls.i.e. there are NO stones
Frances noted that each is listed in the Andreas burial register--unfortunately, I don't have a copy of this (have ordered it)
Unless the burial register lists the grave # for each person, we still don't know where each is buried.
Perhaps others on the board can first check registers for grave #s and/or know if there is some other record at each parish listing the grave #s and who is buried where.
In order to find unmarked graves one would need some sort of cemetery key.

Donna