What hapens if blight strikes?

I was cropping some 2nd earlies and beans tonight and when walking to the gate noticed some potatos on a plot about 50 yards from mine had what looked like blight.  If my 2nd earlies and main crop (valor) get hit what do I do? Do i crop my second earlies before the blight comes they have bulked up and I am getting about 5lbs a plant.  The main crop have loads of foilage and fruit so do I just sit and wait then cut foilage and leave for a few weeks.  Sorry I am not organise to seperate the questions.