The CU came with a 100A Isolator, 63A RCD.
The house is not that big, but long and with 5 foot thick stone walls which make the routes rather tricky - hence so many circuits.
I installed a Consumer Unit several years ago with the following (18-module split-load) layout:-
RCD-protected:
32A Ring 1
32A Ring 2
32A Ring 3
32A Shower
16A Immersion
16A Link to outside shed (without its own CU)
Not RCD-protected:
40A Link to another outside building with own...