"Personally, I know longer think their seeming inactivity matters as much as their threatened activity"

Spot on, IMO. Nice phrase.
I think that's something that needs to be understood.

"Even if the voids did reach the surface the maximum area it can affect is less than the material from the trench they dug for the water pipe."
I've not seen anything that suggests that to me, and everything to suggest the reverse. You've compared area with volume for one thing (tho' I forgive you if you're pissed) and both the area and volume of the material that's at risk of collapsing from the surface seems to be of a different scale entirely on the papers I've seen.

I guess you've seen stuff I haven't though. But it's strange isn't it - everything's vague and unmeasurable and potentially huge, except for the fact that the surface collapse can be accurately given, and it's small. Hmmmm.

"what needs to be stopped is research because the opportunity is supposedly there"

... or at least, that the research donkey doesn't get to ride the repair horse ...
Maybe a better sound bite might be - "Silbury must be kept an agenda free zone..."