well for the radial for example you have to put something like
according to bs7671:2008 the pwer circuit is an a3 radial serving a floor area less than 50m2 using 2.5mm copper conductor t & e pvc/pvc. a B20 A braker would be suitable for this cicuit as thier is not anticipated in rush current. and the breaker should activate before the current carrying capacity for the cable is met meaning it will be protected against damage
along those lines with a bit more info ie tables from the osg as to where you found the current carrying capacity and the table saying it isan a3 radial
hope this helps