Timothy: I have something ringing a faint bell in my head about this subject.
I could be wrong because it was such a long time ago
Many years ago, could be 30 or 40, someone well up in the gliding world in UK did a traffic analysis to counter the CAA argument that there was unacceptable risk of collision if gliders were allowed to fly IMC in uncontrolled airspace.
As far as I can remember the result he produced was accepted by CAA and the practice was allowed to continue.
Obviously the figures from that report would be useless now but if you could get a copy of it from BGA the methodology he used might still be valid.