House extension - new electrical installations

[OwainDIYer]

...
Being Competent requires knowledge of electrical installations, adequate and calibrated test equipment and the detailed knowledge to use it.

No, being part of a "Competent Persons Scheme" requires those things,

It doesn't actually, of course, if the firm is a member of one of the schemes then any modulo-screwdriver-wielding monkey can do the wiring and be covered by the firm registration as far as Part Pee is concerned.