As I had suspected, I had to resort to the world repository of second hand books to start to build up a collection of educational books about the Faith. The first I managed to get hold of is a modern reprint of Fr H Thurston SJ's Lent and Holy Week, originally published in 1914. It is amazingly good. It starts with Septuagesima and the Lenten Fast and traces the history of Lent and the fast, discurses on the severity of the Lenten Fast in antiquity, on relaxations of the Fast, and on whether or not birds counted as meat in mediaeval and early modern times.
Chapter Two starts with Shrove Tueday: as Confession on the day before Ash Wednesday has no liturgical character, where does it come from? and then goes into the difference between Confession, Penance, Reconciliation and Absolution (which four happened at different times during Lent), what happened to the person who, dressed in sackcloth and ashes was banished for six weeks, and how people who weren't carrying out this penance nevertheless began to get some of the ashes sprinkled on them on Ash Wednesday. His description of Holy Week as it used to be are fascinating, though they raise the question about whether those who would return to the pre-1950 Holy Week would be prepared to impose the former strict fast on the entire Church, just so that they could anticipate offices in order to mitigate the fast's severity. The Pian reforms are not perhaps as black and white as I had thought.