You can fill out an Electrical installation certificate if you have a lot of deviations to rectify, you only need to test and inspect the circuits you have work on, just fill out N/A in the parts of the report not applicable and on the front page were you are ask to enter the extent of the installation cover in this report write for example "remedial work to rectify items 1,2,3 and 4 of EICR 12345678" or if there there is only a couple of deviations then minor work certs would be OK , If you are not working or altering any circuits for example securing a loose accessory then you could just identify the remedial work you have done on the invoice to the customer and reference it to the EICR number and observation number.
If you disagree with a coding identified you could also put this in writing to the customer or although sometimes it easier to rectify the deviation rather than trying to explain why in you view that its OK and does not require and remedial action .
15 amp sockets are commonly used on lighting rigs in theatres and my Nan's house god rest her sole