Sounds very odd Charles. Not sure where the British premiere was or even if there was one.
According to Philip Waddilove, who wrote a foreword in Benjamin Halligan's book on director Michael Reeves, the British premiere of Witchfinder General was screened at the Carlton cinema/theatre in the West End of London in early 1968.
The 'permissive society' doesn't exist. I know, I've looked for it - Rupert Rigsby