In the part few months a permanent stain remains in my toilet bowl just where the water enters from the cistern. I have tried bleach and jiff to no avail. Can anyone advise me?
Limescale requires an acid to remove it, bleach is alkaline. Vinegar and citric acid will dissolve it but limescale remover gel would work best. As mentioned above you probably have a small dribble from the cistern which evaporates to deposit calcium carbonate. No doubt you are in a hard water area.