Sorry. Was not getting alerts on this thread. ( ironic ). Lol. It is not a push button it's a fuse black switch similar to the tank ones. Flicks up and down not push button :)
Have you had a sparky look at this at all yet
@Lesley?
I'd recommend replacing the 3 x RCD's under the tank with plain circuit breakers (10A or even 6A). Plain circuit breakers are quite cheap too. I'd then use one of the 16A safety switches (RCD's) from under your tank and install that in place of the plain circuit breaker at the switchboard. This will provide the overall circuit with RCD protection. This coupled with
@Sam Parker 's alarm will keep you covered.
The two remaining 16A safety switches from under tank could also be used to replace any other plain circuit breakers at the switchboard that feed lighting and power circuits that are of the same current rating.