Pete Ashton, Dek Baker and Jez Higgins held a thing called Brumcab back in the nineties, were a sizeable percentage of the uk comics scene was crammed and i mean crammed into a small pub covered in posters and complete with pub quizzes, there was perhaps one dealer table. The second day the upstairs of the pub was not rented and as it were a Sunday it were quiet. Comics folks just turned up en masse, because they knew other comics folks were going to be there. I suspect this is the way it oughtta be, and a definite good template for hosting a comics convention.
Maybe we oughtta throw one. Pick a pub, say theres a comics convention happening there and just wait for everyone to show up.