OP
Ponty Massive
Well it's the same as the JIB saying to lots of lads you aren't a electrician until you have nvq3. It works both ways. Until you have the 2391-10 you ain't a competent full scope spark in napits eyes
Well I guess I'll have to remain un-competent for the time being then!
In a different vein, competency and currency IMO also plays a vital role. Many years ago I did a EITB apprenticeship and did 4 years doing ONC & HNC in electrical engineering. Although I still have the bits of paper (in the loft somewhere), I have very vague memories of micro electronics, motor harmonics, binary logic, octal and hexdecimal, quadraphic formulas etc etc but none of these will help me change a CU. I left the industry for almost 8 years and when I decided to return everything had changed, even the colours of the cables.
Installation competency does play a big role and years of experience helps. Regulations change a lot hense the reason I ask a lot of people for their advise, even the new guys