you have the same multiple chocice exam on the computer, and a written exam-which is basically a booklet with questions and all the references needed all BS's,building regs, water regs, etc, and its basically just showing your working out really, for example you might get a question which asks you to draw a picture of a indirect system, which you go to wras or werever and just draw it and say what reference you got the information from etc (BS 6700 is a big part of level 3 written exams), and working out pipe sizing for cold water pipes etc, unvented design installations, looking at site diagrams and working out drainage points, oh and heat loss calculations, you get plenty of time just dont waste it, learn to know where to look-that is the key of these exams, cause believe me times FLYSSSSSS, good luck mate.