Another can of worms here, Molo..............
As usual with these things, it all depends.
In short, no.
It IS a requirement for new installations, AND alterations to a system. Think of it as with Building Regs. New houses, extensions & alterations must comply with today's regs, but every other building in the country? Hardly!
A "periodic" test must take note of the safety of the system. If any circuit is found to be incapable of functioning safely, then the electrician has to explain this, and give advice on remedies. If you decide to NOT have the remedial work done, then you don't get your certificate, and the system is marked and recorded as unsafe.
It may be possible that he found such problems with the four circuits. If so, protecting them with an RCD may be a solution.
From what you say, I guess not. Assuming all circuits are sound. That's the end of it ............ certificate issued but noted to advise on upgrading.
Many electricians are honestly confused over the requirements. Some are exploiting this confusion by recommending, and making work for themselves.
What they're afraid of is that their work is occasionally inspected by whoever approves them (NIC or whatever) ......... so they play safe.