Many thanks everyone: keep 'em coming! I'm already getting some very interesting patterns emerging (and, as I suspected, the UK ban seems to have played quite a role in fostering the film's cult status).
One other thing I am wondering about "Django", which some of you may be able to help with: does anybody have any info on its release patterns in the US? Howard Hughes writes that it failed to gain a certificate there, but I have received some responses from the US stating that it was shown in cinemas in the 1960s. Was it perhaps released in grindhouses only?