Hi, pjs12 and GrahamH,
Thanks again for your thoughts - they are much appreciated. I have another photo that I am attaching which better shows the area around the grave. What you suggests seems to apply here - there is no grave immediately to the left, right, front, behind.
There is no sign of railings and I am pretty sure I would have noticed them underfoot at the time but as you can see, the grass was a bit high that day.
The Church itself is no longer in daily use, so I think I will have to follow-up with the Record Office. In contrast, however, the Churchyard is still in use so I'll have to research that part further.
By the way, I said the burials were 1850s but they are actually 1870s. Probably not crucial to know that but I should correct my mistake.
Thank you once again for your interest and support.
Best wishes.
Simon