So as an inspector, you've completed your report, assumed the installation was installed to 15th edition then someone informs you that it was in fact installed to say the 16th edition, are you then going to alter allocated codes and defects comments? Of course not!
Check pages 4 and 5 of the ESC guide below and indeed Guidance Note 3-both publications categorically state that the installation is to be tested against the requirements of the edition of BS7671 current at the time of the inspection.
Of course there will be non retrospective changes between editions, that's why we have a code system based on assessment of risk.
http://www.esc.org.uk/fileadmin/use...y/best_practice/BestPracticeGuide4-Locked.pdf