Pretty sure I've seen newer MCBs fitted to those old MEM boards, but I wouldnt advise it. TBH I would look at getting the funds together to replace that board. It has a single point of failure for your entire house (that RCD). Nowadays we individually RCD protect circuits so there is no single point of failure. If a circuit trips, only that circuit looses power.
Does the garage consumer unit contain an RCD main switch? Take a picture of the whole thing.
Does the garage consumer unit contain an RCD main switch? Take a picture of the whole thing.