You're right regarding the ad-hocs, most do / did operate during the daytime, or early evening. And of course the FedEx nightly operation was just pushed back to arrive immediately after the runway reopened each day.
It's a shame the airport doesn't take the same pride in the cargo business as it does in passenger numbers. I would have thought they would have been mandated by the CAA to provide (accurate) figures for both pax and cargo.