The 16th Edition can be roughly split into 3, in 1991 it was not BS7671, that started as BS7671:1992 so that was the first edition of BS7671. So yes, can see that complying with BS7671 can't be items changed before 1992. In BS7671:2001 when it came out was considered as the 17th edition, as there were many changes, and when in 2008 we got BS7671:2008 that was the point when near all items in the home needed RCD protection, but the major change was the change in bonding requirements, mainly in the bathroom, which now makes it hard to ensure compliance with any edition without RCD protection, as it is all too easy for bonding to be lost, due to plastic pipes.
But each edition has a clause something like "Installations designed after 30th June 2008 are to comply with BS 7671:2008." so we need proof of the design date to show compliance, fortunately we are not required to show it ever complied. And I noted my parent's house, built 1954 had wall lights, which were not earthed, 13th Edition did allow not to earth, but it did require "(ix) Lighting fittings using filament lamps installed in a room having a non-conducting floor, mounted at such a height that they cannot readily be touched and are out of reach of earthed metal." so it would not have been allowed under 13th Edition to have non earthed wall lights, and to get filament lamps today would also cause a problem in most cases. However, the house may have been built under the 12th Edition, but one would need to see the installation certificate, which I have never seen, and my last house built in 1979 I never got an installation certificate, and it was not until BS7671:1992 that we started to see installation certificates issued.
But code 4 was dropped, so it does not really matter what BS7671 says, as the inspector we have to decide what is potentially dangerous to personal, so lack of SPD is only a danger to equipment, but lack of RCD's will. But only where one could get into contact with live parts, so if a rental agreement does not allow drilling of walls, then cables buried in the walls present no danger. However, in real terms the inspector is unlikely to view the rental agreement, so would have to assume drilling could take place.
On finding a fault, the inspector has three options, correct it, report it, or disconnect it. Once coded as a code C2 or C1, it needs correcting, with a rental, but owner-occupier can simply ignore it.
However, I was more looking as what I do in this house, without really thinking about it, renew switches for smart switches, also some sockets, although today more likely to us an adaptor, swapping outside lights from 500 watt halogen to 12 watt coach lights. Adding the odd socket, completely changing how my central heating is controlled, and also powered as not backed up with solar and battery. And even items which would be strictly speaking illegal, I actually got a scheme member to add 4 sockets in the kitchen, but I would have had it not been part of the solar installation, and I think most people would fit sockets in their kitchen, even if strictly speaking here in Wales it is notifiable.
