Hi Ocifant,
I've just had a reply to my email from someone in the 'Heritage Information Team'. Following my email he has been in contact with the English Heritage Field Warden. She already knew that the stone was down (apparently it's been down for 'some weeks') and is arranging for the socket to be excavated prior to re-erection. Apparently an EH archaeologist will be going over the site in the next couple of weeks.
Gun Rith is a scheduled monument, so that's going to help with this process. A lot of the standing stones in our area aren't scheduled, and some have disappeared over the last 50 years, presumably in part because they weren't protected. This pisses me off a bit, which is why the fall of the Gun Rith stone struck a chord.
Kammer x