Polarisation, position angle and flux (in arbitrary units) for the some of our targets as shown by the labels. Red symbols refer to data obtained with the order-separating filter GG435, blue symbols to the data obtained with no filter. In the plots showing the polarisation, the black solid line is the best-fit obtained with the Serkowski curve on the average data, while in the plots showing the position angle the black solid line shows the best-fit obtained with a first order polynomial. Green solid lines represent flux non corrected for the instrument and telescope transmission functions.