Approved document P is just a downloadable document that is to do with the building regs,from a-z,P is the electrical part,L is energy conservation,if you buy the electricians guide to the building regs all will be explained as to what affects our trade.You really could do with the 17th edition,i cant see why you couldnt sit the exam as its multi choice gola exam,but only a college or centre would know.You can buy niceic installation/test certificates from there website(green ones)they are for non members,Domestic installers use purple certs,approved contractors red certs,these look better than copying from the net or buying the cheap nasty ones from the wholesalers,take a look around the forum as there has been endless discussions on this exact topic many times.