Before, it was the gas man and now it is the electrician’s turn to milk the landlords.
I am afraid it is mandatory to have the electrical certificate and have the work done.
Every inspection will fail but if you make an agreement with the electrician, he will pass it and give you a certificate for 3 years. Next time you have to have it done, tell them that you need RCD installed and then the inspection certificate. It will work out cheaper.
Wait till the fun starts when the powers that be makes metal boxes illegal for two years and then metal box legal 2 years after that.