Could some please clear up the facts concerning Consumer board change to a domestic property when no additional circuits are being added.
Old fuse board is rewirable
a) Do all circuits have to be RCD protected? e.g. lighting
Quick answer no. But in most cases everything will need RCD protection because of the cable. If the cable is buried less than 50mm in a wall or ceiling from either side then it must be either one of the allowed cables like Al-tube or protected by a RCD and in most cases the cables mean RCD's are required.
Sockets under 20 amp except for ones with special designated use need to be RCD protected. And also everything inside a bathroom also needs RCD protection.
The number of RCD's is also open as provision must be made so one circuit is unlikely to effect another. As more and more RCD's are added so there is less and less chance of one circuit effecting another. It is also required that a fault on one circuit will not cause danger by tripping out another, this part of the rules is not really new. But many electricians had not interpreted the regulations as also meaning the RCD as well as MCB now this has been clarified but still it is down to some interpretation as to if twin RCD's will cover the requirements or if every circuit should be protected using RCBO's. With the latter it is easy but where using only 2 RCD's then really some sort of risk assessment is required to show consideration has been made as to any dangers due to a RCD tripping. This risk assessment would then need to be made available to anyone adding or removing safety items. For example in my house the light illuminating the stairs and the consumer unit are battery backed.
But I have never written a Risk assessment and if I was asked where the 10 year inspection and test was I would have hard time finding it. I know I have no ELI reading for one of the pair of RCD's as the tester always trips the RCD yet never trips the other one and both the same.
The BS 7671:2008 is not law. And the local authority building control do not follow it otherwise they would as the competent person responsible for the safety on the site need to sign the installation certificate which they are not required to sign. Yet they at the same time want others to sign it. Also all the regulations are in English although they state the signs required under the regulations must be in the language/s of country where items are used or sold. Which means it can't be enforced in Wales as a law although one would be considered to be negligent if one didn't follow it. So is another one of those where if some one was injured it is up to courts to decide.