The L98 A1 cadet gp rifle is not a scaled down version of the army's SA80 it is an SA80. Its has exactly the same dimentions. SA80 was a weapons programme, small arms for the 80's.
The L98A1 is simply a L85, or SA80 as it is commonly known, with the gas parts and change leaver removed and a cocking arm fitted.
It fires the standard nato 5.56mm round and holds 30, the same as the army, in a curved magazine.
L98A1 Cadet GP rifle. simple.