I'm having a hard time visualizing the scale of things in the 15th century british isles. People tend to generalize "medieval times" into one stagnant point in time, so I run into confusing scenarios along the lines of...
"soldiers were elite warriors hired on an individual campaign basis. people grouped up in towns accompanied by a fortress inhabited by a battle-trained warrior and maybe a friend or brother with similar combat experience. He would then dictate the actions of his people in order to fend off and discourage attacks."
that's all well and good, but then i look up professions and jobs from the time, and I see oddly specific, high-population jobs like "catchpole" - one expected to find people with debts and make them pay up.
How could a civilization small enough to be dictated by a knight and a handful of castle-dwellers have enough debtors to keep a catchpole employed?
I'm also unsure about when the law stopped having trials by combat, fire, water, and exile, and started imprisoning people. I've heard that prisons were once reserved for nobility that you don't want to risk hurting if you weren't certain of their guilt, and eventually there was a shift where the nobility would be exempt from prison when awaiting their trial.
What would an average 15th century town look like in terms of architecture and population, and at what point did stone masonry begin to dominate cities, leaving any plant life as negative space?
In terms of population, towns are small by our standards, though remember this is around the population low following the Back Death: apart from London with 40-50,000, only Bristol and York can be said with any confidence to have exceeded 10,000, followed by the likes of Coventry, Norwich, Lincoln, Salisbury, King's Lynn, possibly Boston, Colchester and Beverley, and later Newcastle in the 5-10,000 class. A large provincial town like Stamford, Newark or Derby might have only 2,000. In all there may have been a quarter of a million people in such places, a tenth of the population, and perhaps as many again in the hundreds of smaller settlements distinguished by their markets but often also retaining village characteristics.
Construction would largely depend on where you were: stone if it was readily available, but generally timber-framed houses and many civic buildings. Towns generally possessed lands outside their boundaries: besides the churchyard, some houses retained narrow rear strips that might be used for growing food or keeping animals, but many must have relied on remoter holdings or gone without.
The hundred-plus boroughs already had their own governing institutions, so even in towns as small as a thousand inhabitants the days of lords dictating to all & sundry were drawing to a close, though the local authorities themselves remained largely self-perpetuating elites.
Trial by ordeal was gone, and by combat on its way out, so there would be detention facilities for those awaiting trial: these didn't have to be dedicated prisons as non-capital sentences would more likely to be of mutilation, branding, the stocks etc.
Stephen Alsford's wonderful Medieval English towns site has everything you need. Check out Colchester for its illuminating legal tussles with local landed bigwigs, in this case the abbot, elsewhere the lord.