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If you had done the installation in the Kitchen and you are not registered with a domestic installer scheme ( google competent persons scheme)
You would need to notify building controls prior to starting work
https://www.diydoctor.org.uk/projects/partp.htm
After an application has been made and fee paid, you will be given the go ahead to start the work.
Building controls will then inspect at first fix, cable sizes, routing of cable, support, fixings etc..
Then if that is okay you will then be allowed to continue to the next stage, second fix.
Before the installation is energized building controls will then inspect and test this installation, if that complies to the relevant standards it will then be signed off and certificates will be issued at a later date.
This is a legal requirement, your installation must compy to relevant standards or it will not be signed off. If this is not done it is likely you have broke the law and your house insurance will also be invalid.
You'll find electricians are unwilling to sign other peoples work off as they yhen take on responsibility for that installation.
If a registered electrician had done the installation in the kitchen, they can then self-cert it with a EIC (electrical installation certificate) they will then inform his scheme provider of the work and they will forward that to building controls.
An registered electricain can again install a new CU, issuing a EIC but any deviation from BS7671:2008 will be made on his report, they do not have to pass off, the work in the kitchen. This report again goes to scheme provider, then Building Controls.
Hope this helps
KB