You are making me absolutely starving!
And yes, high tea is, or was, well known in Scotland, Northumberland, Yorkshire, and probably Derbyshire as well, but not in the south of England.
In my Scottish childhood (1950s-1960s) my grandparents' generation ate breakfast, usually porridge, followed by toast and marmelade, accompanied by tea before work, whenever that started.
Dinner, two courses, usually soup followed by a meat or fish dish with potatoes and a vegetable at noon. On high days and holidays, pudding of the boiled variety instead of soup.
Afternoon tea, if served at all, consisted of tea with scones and biscuits or a sliced cake, and only on special occasions sandwiches.
High tea as described above, at the end of the working day.
My parents' generation moved dinner to the place of high tea and ate a cooked lunch at midday, incorporating in it a good deal of what their parents had served at high tea, but usually in lesser quantities. And many of them drank afternoon coffee in preference to afternoon tea.