Can't give it a code 2 because there is nothing in 7671 wrt asbestos.
That is there is nothing that says asbestos materials don't comply with 7671.
You must notify the customer, best way is an associated comments section appended to your PIR.
Thing is with a code 2 that infers that it could be electrically dangerous, it is not.
In fact if left undisturbed even under CAWR there is no reason to change.
HOWEVER, the client if commercial or a private or social housing landlord MUST have an asbestos survey a copy of which MUST be given to any persons likely to come into contact with the asbestos and this MUST detail ALL asbestos in the premises including that in electrical switch gear.