There are two aspects to this.
To cover your landlord duties, if there is only one C2 there for a non IP rated bathroom light then just get another sparks to change it (it's not an expensive job or expensive light), and as long as you have a document saying it's repaired you have done what you need to do in terms of meeting the requirements of the legislation. You are then sorted for 5 years.
But the other aspect is I'd be quite concerned the inspection hasn't even looked at the supplier earthing arrangements or intake. It might be the supply for the flat is in a common area he didn't have access to, but this should have been noted as an operational limitation if so. Is it possible to see the whole report with the property and contractor details blanked out?