Just to clarify, Schools were never classified as MT it was just that the centralised BR organisation couldn’t understand that a 4-4-0 could be an Express engine so they were painted in ordinary passenger lined black. When the regions were given more autonomy in 1956 the Southern corrected that and lined green became the livery but 30900/914/919/932 remained in black until withdrawal. The situation with pannier tanks wasn’t that simple. One or two 5700 and 9600 class were given mixed traffic livery, the standard livery for the passenger classes 5400/6400/7400s was lined green from 1956. Britannia’s were always intended to be Express passenger locos and were liveried accordingly as were the Clans.