@flameport is correct, and this is some thing a few people have referred to, if as it seems it has never complied can you go back to whoever fitted it?
Today we have RCBO's so likely other than missing lid does not need a new consumer unit. But the box plus a surge protection unit for a cheap make around £90 and £18.60 for each RCBO, but Hager RCBO around £24 and the SPU £126 plus of course a box for the SPU as not enough room in the existing consumer unit. So parts to keep to Hager will cost over £112 more than complete new box. So big question is it worth keeping the old box?
The wiring regulations are not retrospective, but it seems it has never complied so you can forget that.
So the question is if it is likely to become dangerous? This is not so cut and dried, however first thing I did with this house was put in RCD protection, so can't really say if there was a potential danger, but when the roof leaked it did trip so yes it could have caused a fire without the protection, so can't really say the inspector is wrong.
So what is more to the point is what to spend out, on this forum you will see debates between RCBO's and RCD's plus MCB's. The RCBO is less likely to nuisance trip, and if it does trip less likely to require emergency attention to correct, so electrician Monday morning not Sunday at 9 pm, so can cost less in the long run, specially if you add a freezer full of food, but some say they have never had it trip. And it is over 30 years, so once every 10 years.
Putting just the freezer circuit on a RCBO could be enough, or maybe freezer and the lights, so may be 5 MCB's on each RCD and 4 RCBO's but then looking at 22 module wide instead of 18 module wide for RCD instead of all RCBO's. But this is what you need to consider, you need a new CU that's the simple bit, but what new CU and can you claim from person who fitted last one?