With respect to the practice being continued through the Peninsular War, the “Return of Officers entitled to a Medal or other badge of Honor, in commemoration of the Battle of the Nivelle, on the 10th of November 1813” (TNA, WO1/202, pp.191-194) lists commanders of “Lt. Battalion” after commanders of other components of nearly all British brigades. However, this is not the case for Brisbane’s Brigade which already included three companies of 5/60th, but their CO is listed and I am assuming that he also commanded the light companies of the other battalions if required. There is also no specific light battalion commander listed for those brigades of the of 7th and Light Divisions containing battalions of regular light infantry or rifles. Bar for one Lt. Colonel, all light battalion COs are Majors.
Cheers, Andrew