a lot of my links above go to my map. It is all derived from one database, map location is via OSGR which can be displayed along with Post Codes, each of which have a (pointer) map hyperlink underneath. If the venue & map marker disappear, I have taken the venue off the list (usually due to information received). This is not a "fit and forget" endeavour. My information comes from local enthusiast's e-mails, and asking people who "go" when seen at Festivals etc. And the area covered is deliberately kept "doable", places I might drive to. No further. And I link to anyone with good information, on the periphery.

FWIW I update constantly as information comes in, always carying a datestamp. I am wary of copying from other websites, especially if the audit trail can lead back to me. That would create a self-supporting loop.

The problem implicit in FreddyHeady's post and other Folk Maps is that information is not always updated. Indeed when new, the organisers blitz all modes of free publicity, then forget they did that. When the session fades and people loose interest, publicity regarding cessation is not high on the agenda. Crowd-sourced data is like that.