Ha! Ha! Aren't our regs great !!!!!!
So many good points, right not in any particular order
Slightly picky answer and a play on the English language - You do not 'require' a certification 'when' you sell your house, you should
already be living in a certified and tested house and have either an Electrical Installation Certificate (EIC) or Periodic Inspection Report (PIR) in place to cover the installation. If this is under 10 years old you're covered, however it 'looks' better if your house has just passed a Periodic because it gives the buyer the impression the electrics are safe. A domestic dwelling should be tested every 10 years (max), 5 years if commercial or even less if the installation is in a harsh environment or liable to change or abuse (farm yards is the classic example - those farmer boys love nails for fuses

and have never seen a rodent eating a cable.
You are correct for rental properties a new full Periodic test
isneeded when vacated and before new people move in.
Competent Person - horrific term - in the electrical sense this does not mean someone 'who is competent'. It means someone who can prove their competency (with qualifications eg City and Guild 2391). How could you stand up in court and show that you knew what you were doing, you would have no defence.
As an aside - when I did my 2391, I was told that I would be considered guilty in a court of law unless I could prove myself innocent by issuing a test certificate for any work I did or I was the last electrician to touch an installation and someone was hurt - even if it had nothing to do with me. e.g I change a downstairs socket for a drink for my mate down the pub and his daughter was electrocuted using the upstairs shower some months later, I could be on a manslaughter charge with no defence because I couldn't prove what I did or didn't do.
Wiring Regulations and the Law, I don't fully understand this, but basically it goes something like this. The wiring regs are not law but they are incorporated into the building regulations and I think the Health and Safety legislation which ARE law therefore they are a legal requirement. - Something like that.
I'm not entirely sure you're correct - the regulations, I believe, still contain regulation 12(6A), which requires notification only for new circuits, replacement of the consumer unit, or addition or alteration to circuits in a special location. Outside that, no notification is required.
Yes you are correct with this one however it is a difficult one in this context and is ultimately down to the person doing the test. Effectively it is a new circuit - but it's not. In context to the OP I do not know the background of the installation he was talking about. For his house insurance, selling his house in the future and local authority purposes notification from a Part 'P' registered spark would only pay what £1.50 online to ensure his customer (and himself) was covered from all angles. The circuit sounded like it was massively f**ked around with adding many more points on it than it originally had and the functionality had changed. Earth leakage implications, tripping characteristic would need to be addressed which would be fundamentally different to what was there before. The only original part of it was two legs back to the CU. To be fair you are probably correct with a minor works but I am not standing in a guys house with a coffee having a chat but on a pubic forum not knowing who might read this in the future and takes things literally.
I would still prefer to tick all boxes in
this application. Label up the CU with Lab Supply and notify. If the guys house burned down from an unrelated fault the new lab's electrics 'would' be blamed - no cert - no insurance pay out.
I'm not 18th Edition, but I believe there is now a provision for a spark to 'sign off' other peoples installation which was what I was getting at in the post. To me it's a no brainer.
All the annoying legal bollocks aside, assuming there's no intention to supply more than 3kW, I see no problem with a single FCU supplying as many sockets as desired.
I agree, but again were not chatting personally in his house, its some things to for him to consider and discount as necessary with his sparks.
This is a fixed installation, no matter how unpluggable it may be, and all the requirements of BS7671 and the building regs apply.
I disagree - though there's no way in hell I would install this in walls on a professional level, it would allow a DIYer to do his own install and comply with regs. If this was an extension lead screwed to the wall what's the difference? If this was in flex feeding sockets via a stuffing in the end of some dado trunking or any trunking come to that, what's the difference? I don't have my (17th Ed Amend 3) regs to hand but I can't think of anywhere where it states you can't. You don't test extensions cables do you. They rely on the protection offered by upstream devices RCD's, MCB, Fuses as applicable. What if you have a flush FCU, back feeding a boiler with a cable buried in a wall is the boiler part of the fixed installation - No, it' is an accessory. You would disconnect it when carrying out out an Installation Resistance Test! How about a 240V thermostat with cables buried in the wall - again we don't test. There are many instances like these which are not part of the fixed installation.
If you know of a
specific section dealing with buried cables
in this context I would be very grateful if you would let me know.
Remember the regs are not written to be verbatim they are a written as a guide to professional electricians enabling them to use their judgement to comply with the law on their installation given certain criteria. And for the record I am uncomfortable and REALLY squirming writing all of this bit
You could collect the changes (and 'repairs' .. I think you're allowed those) and do them all at once.
ish!!! Other than replacing like for like, Every piece of electrical work needs or should have had certification of some sort when installed. The killer is the change in colour codes to 'harmonise' with F**cking Europe so this dates your installation. Any new Brown and Blue core cable with Grey outer sheath cables is post requirement for certification and notification. The government has done an absolutely piss poor legislation job with no notification to the public - unlike Gas Safe and Corgi before them.
You ask the average man in the street about Part 'P'. If you do get a positive response they think it is a qualification not a £750 odd/year club with the government tracking how much work you notify online to estimate your tax returns.