Hello Shelagh There is a very large linen map in the St. James Cemetery Archives in Liverpool library, with every grave number in its correct place. I was told that when they 'cleared ' the graveyard, the stones were moved 'outwards' or to the side in a direct line.
That is how I found the grave of my Borrowscale ancestors. It only took me my lunch time one day to trace it. The number of the Borrowscale grave number is 1702 ssection D I think.
Good Luck in finding yours.