I live in UK also. 100A fuse on meter tail from the grid is pretty standard in houses. It’s that size to protect the cable, not that they anticipate you going anywhere near that much.
Breakers on different circuits after that will be lower eg 30A.
You are unlikely to go above 50A total unless you do something like turn 6 electric kettles on at once.
I am planning to use a 50A Shelly EM on my main meter tail. Presumably above 50A will clip the reading rather than damage anything.