My personal opinion is that regional lists work best for metropolitan area scale coordination
Now onto the vexing questions of whether the uk is a region at all, why regional-uk would not work for the poor folks in the Isle of Man, why London, Ohio, USA folks are always late for regional-london get-togethers, regions where abs would deliver vaxen to, etc
Best,
Alistair
PS. If there's a good crowd anywhere who would benefit from a (metro-area?) mailing list for coordination, let's hear about them