cheap ballasts do get hot, but it shouldnt get too hot to touch.
your in the uk, so make sure your ballast has a " CE " mark in the documentation, or on the equipment lable, it should only get about as warm as a high power hi-fi amplifier.
if it has a heat sink attached ( like fins or paddles for despersing the heat) its normal for that part to get pretty hot...just make sure theres good air circulation so the heat can be dispersed.