Had it frequently in school as a pupil, and then as a teacher, in Kent. Selected bakers will sell it, which is better than making it, because you do not have to eat the whole thing. As a pupil, we were given it in rectangular trays, to be shared between eight girls, half of whom abjured it. I used to eat about four portions "to finish it up". As we walked vast distances between school buildings, this did no harm at the time.
When I was teaching, I got the recipe from the school cook. She did not include egg in the pastry. Nor specify muscovado sugar, though when our bakery was taken over, they had heard that was the sugar to use. I have used soft brown sugar, both light and dark. Nor did I whisk the sugar and evaporated milk together from the start, but did the milk first and then added the sugar. The cook did not suggest refrigeration after setting in the oven - I suspect it was a good way to use the declining oven heat after cooking something else.