Beverley
Found it. I was rather surprised, as lots of graves in C section do not have headstones. But the Paterson stone is there, albeit lying flat (perhaps pushed over by vandals, as a few headstones have been).
The inscription reads:
Erected
in memory of
Janet Whitson
wife of William Paterson
died 10 Jan 1889
in her 70th year.
William Paterson
their son
died 7th Sept 1895
aged 49 years
also Annie Edmond his wife
who died at Leith 25th Feby 1899
also the above William Paterson
who died 6th March 1908
in his 86th year.
Also James their third son
who died at Liberty Hall 14th Decr 1916
aged 66 years.
On Rootschat I found reference to the baptism on 3 May 1846 of William Paterson, son of William Paterson and Janet Whitson, Pencaitland. (The Rootschat thread was running in April 2008 and can found under: "Canada / Chinakays 'Two For One' Scavenger Hunt. Please Join In". The thread makes reference to several baptisms of different William Patersons, and the thread is not about your family.)
Liberty Hall is at Gladsmuir, a few miles from Haddington. I think it's the name of a farm.
Hope that helps with your research.
David