In england most of the lighting switches are installed with the following loadings;

Crabtree plate switches; 6amp or 10amp
MK plate switches are now 10amp
some other versions are either 6amp or 10amp

some grid switches, cover plate/grid/switch/back box these range from 6 amp 10 amp 20 amp

depends on the load you wish to switch.

Hope it helps

John H