You begin dealing with that by saying "I'm not paying you a penny because of your incompetence and your inability to understand the regulations which you, as a professional, are bound by.Quite often Gas safe engineers will not commission a boiler without (unrequired and unnecessary) so called cross-bonding of all the pipes connected to it.
You can argue your case but it they won't sign they won't sign.
There is.E.g. "Electrical equipment shall be installed in accordance with the instructions provided by the manufacturer ..."
There is no provision made should the manufacturer's instructions be unnecessary or just wrong.
There is the paragraph on p2 which points out that people must rely on their own skill and judgement when using the publication. And the one lower down which points out that compliance with a B.S. cannot confer immunity from legal obligations (e.g. EAWR, Building Regulations, CDMR, not to mention anything contractual).
There is also 133.2 and 133.3 which could easily be taken to indicate that the choice or installation of equipment which when installed according to the MI creates a breach of the Regulations is in itself non-compliant.