Someone who is registered under Part-P (spit) can self-certify that their work complies with the standards. The customer then gets a certificate through the post (there may be other mechanism) depending on which 'club' is involved.
If the work is not done by a registered electrician then Building Control will issue the certificate of compliance.
:::::::::::
PVC Sheathed Twin and Earth may be clipped to the skirting board. Behind the skirting would be unacceptable except in the 150mm nearest a corner or protected by steel armour plate or more than 50mm deep.
This would quite probably be a good way under kitchen units but not elsewhere on a visual aspect.
================= Comments have been made in this NG about the insurance aspect.
The track record of insurance companies suggest that they would try to avoid paying out if fire (or other) damage could be attributed to electrical work not properly certified. Part P is a 'bogey man' for DIYers, so it's worth getting the bit of paper for peace of mind.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.