Why not simply, "C2 - contravenes Regulation xyz.a.b?

The customer will need to get an electrician to remedy the defect and that electrician (could be you) will know what it means.

that electrician (could be you) will know what it means
Maybe.  I fear not all electricians have that good a memory or carry the regs with them, or if they do they certainly do not read it.

And I think it is setting up the wrong sort of relationship with  the customer.

'you have something wrong with your system you need to pay to be fixed  but don't bother your pretty head about what it is, just fork out '

Next thing of course is all electricians are part of Rip -off Britain culture and the reputation damage.

I'm with JP though that  If at all possible a plain language explanation should be given.

' inadequate earthing of bathroom lights' is the sort of thing that semi technical folk stand a chance of grasping, as opposed to some elitist sequence of digits and dots that for most folk might almost as well be the numbers of the  Space corps directives from Red Dwarf. (*)

Mike

PS
* to save those who do not know.  the effort of looking, the SCDs are at about this level. One of those is ours - can you spot which one ?

(147. 'Crew members are expressly forbidden from leaving their vessel except on production of a permit. Permits can only be issued by the Chief Navigation Officer, who is expressly forbidden from issuing them except on production of a permit.')

(411.3.2.“Metallic pipes entering the building having an insulating section at their point of entry need not be connected to the protective equipotential bonding.” )

(7214. 'To preserve morale during long-haul missions, all male officers above the rank of First Technician must, during panto season, be ready to put on a dress and a pair of false breasts.' )

The third one (7214) is the correct one. The other two are obviously just made up.

Design considerations - there are three adjustable adjustment wheels for trimming and there are ten non-adjustable adjustment wheels as well. The non-adjustable adjustment wheels must be suitably adjusted before commencing the adjustable adjustments accordingly. Once premium adjustment of the adjustable adjustments are obtained then the non adjustable adjustments must be adjusted further until the premium setting is obtained

The third one (7214) is the correct one. The other two are obviously just made up.

Design considerations - there are three adjustable adjustment wheels for trimming and there are ten non-adjustable adjustment wheels as well. The non-adjustable adjustment wheels must be suitably adjusted before commencing the adjustable adjustments accordingly. Once premium adjustment of the adjustable adjustments are obtained then the non adjustable adjustments must be adjusted further until the premium setting is obtained