Hi Bridewell,
I don't know this particular graveyard at all at first hand, bar the photos on this website and other online images, so please excuse my ignorance.
Please clarify or confirm the following;
I think you're saying Mr Trevor Harvey was at/near the Church itself in Coleford, and not at Gloster Archives, presumably the same man who helped write this http://www.christchurchfod.org.uk/cguide.html
Oops I now see he's the Churchwarden, sorry ! http://www.christchurchfod.org.uk/team.html
So clearly you've already done the right things and seen the "local experts" including the vicar and best of all had access to a graveyard map etc.

I presume you then searched the graveyard pre-armed with this information, presumably you were able to locate the approximate area of the graveyard where the book indicates your grandmother was buried ?. Are there other graves nearby - if so were they also on the map ?. I ask as this could help ensure the map is correct and you're correctly interpreting both the map and the book regarding plot number etc; i.e. ensuring you were indeed searching the right area based on comparing against other referencing "landmark" graves nearby ? How confident/experienced was Mr Harvey with the accuracy of the map, and interpreting the plot reference numbers, sometimes these aren't as logical as it may seem ?

In the apparent absence of your grandmother's grave, I'd want to search for other graves, especially those whose burials were recorded on the same page as your grandmother as they were presumably at the same time and the same part of the grave yard. This might then indicate if an apparent unmarked gap between marked graves was hers, for example.

Do you know if the grave was marked with a stone ?. If yes, is it likely to have become eroded and unreadable with time, compared to others nearby ?. It's not as if it's a particularly ancient one, but some stones do suffer from the frosts etc... ??

Is the part of the graveyard where you looked still in good order - not overgrown, grave stones in place, etc ?. Were other stones readable, assuming they were a similar age ?.

It might well help if you can please post the burial details here; especially as the current weather is so good if anyone lives locally they might enjoy a wander thro the graveyard before wet weather arrives (sadly I'm not local at all).

Are you local to Coleford area ?.

Many thanks Jeff.

Could you provide the name(s) of the person(s) you seek please.

Mike