Agree wholeheartedly with Genghis on this - a couple of years ago I was returning from the IOW and thought I'd route overhead Goodwood. On contacting them before crossing the coast they informed me that there was a freefall parachute drop about to take place from FL100, so it was no trouble to avoid it.
I hadn't picked up the details in the NOTAMs as I hadn't intended to route that way.
As I recall, I heard them mention the drop to another aircraft before I made my call, so even listening on the frquency can be beneficial!
SD