Never went to any film fairs, but back in the early to mid 90's me and a mate used to go up and down the country to record fairs and there was always a couple of guys selling VHS's from under their main CD/vinyl stalls. Being a horror fan, I used to get them to show me the tapes they were selling, but being between 12-16, they never let me buy anything
I saw some belters too, pretty much all the DPP39 titles on both Beta and VHS, decent enough prices too-£20 each etc.