Light Tea is a lighter version of Afternoon Tea with a scone and a sweet.
Cream Tea is one where heavy whipped or clotted cream is served to spread on the warm scones along with strawberry jam. It doesn't refer to the milk you put in your tea.
High Tea is most often served as a Full Tea, only more of the same. It is enjoyed at approximately six o'clock and is a light supper for the family or a before-theater meal. An entree such as chicken a la king