Ahhh my fave Broad Bean.
Yes they can take a little while longer. Another method by the welsh chap who was the radio years back, was it Terry Walton? Anyway his method was to pop a little damp compost into some plastic bag bags, pop say 5 seeds in then tie up and keep them in a warm place, he used the airing cupboard at home, he then start to check their progress after the third day, once the shoot had appeared he would transplant to a pot.
I normally sow mine in Jan, they are tough cookies, mine are now full of flower and pods are not far away and not a blackfly in sight