As others have commented, it's hard to make useful suggestions if it's not really clear exactly what are the specific concerns of the FC Dorset.
I understand that they are seeing an increase in caches placements on their land and I was just wondering whether they also get notification of caches which are archived? In other words, is their perception all in one direction? (Or perhaps very few caches get archived?
)
I was also wondering whether anyone at the FC is accurately collating the information about the new caches as they are published. Although you say that they get informed of the OS references, I wonder whether perhaps this just gets dropped into a large file somewhere, marked "Geocaches", and all they see is this file getting thicker and thicker!
Would it be of any assistance to them if, say, twice a year, someone* sent them a Memory Map overlay of the "current state of play", of active geocaches on their land? Something they could pin on a notice board for easy reference?
My apologies if this would simply
not be feasible due the number of areas they actually manage and the time such a task would take for the someone* involved!
*
Definition: An individual with time on their hands, or one who draws the short straw.