How encouraging to read these posts, showing that I am after all not the only one to feel such an anxiety in poor vis.
Yesterday I flew for what was in any case to be a short local flight, well aware that wx was 4km and sunny. But once airborne I restricted myself to four circuits and came in. Like a number of others above, I agree that 4km vis is insufficient for me as a once- or twice-a-month PPL - I like to enjoy my flying.
Never mind, I'm off to Oz in May for 14 days of flying touring in fantastic conditions!