Graeme.
Like yourself this is a never ending problem for us, and the only solution we have is to note on the certificate that the paperwork for the electrical supply has not been seen, and note any spotted deficiences.
We now send our panels to site with a compliant double pole, etc, etc...spur in order to save the sparks having to do the last minute rush, which although we never really charge for it, does gain us brownie points and (sometimes) allows our commissioning engineer to say that he has seen the paperwork and it is compliant.
We do however have one job, local authority, where the panel was commissioned 9 months ago, and still not been turned on as their sparks havent put power to the panel, (we offered to get our man in, but he wasnt approved by them!?!).
Bill