Installations almost always have a total maximum load that may seem to exceed the supply rating, if all the fuse/over-current device ratings are added up. In practice, there are rules of thumb used to estimate the likely maximum load, using a principle called diversity. Diversity assumes that not all loads will be on at the same time, or if they are on they will not be drawing their full rated current. A set of commonly used diversity rules are given in the IET On-Site Guide, from which I've cut and pasted the table below (assuming fair use applies and the IET won't get cross . . .):
View attachment 622389
Although charge points aren't yet mentioned in this 2018 table, it has been confirmed that no diversity is allowable for them - like water heaters and electric heating, the assumption is that they will operate at full current all the time they are active.
Finally, the main purpose of a fuse or other over-current protection device is just to protect the cable it supplies, not the equipment at the end of that cable. Over-current devices have to be sized to protect the size of the cable, as de-rated for its particular installation conditions. This means, for example, that a single run of 2.5mm² T& E, run as a radial, a cable that has a free air current rating of about 27 A, may need to be protected by a 16 A MCB if it is run under 200mm of loft insulation, as it will be derated by a factor of 0.63 because of the insulation.