>>64498201
(not the other anon)
The war ends around 1453 (conveniently almost co-inciding with the fall of Byzantium, so a useful demarcation of the true end of the Middle Ages).
Both England and France spend the next 300 years mostly consolidating power by taking over smaller proto-nations. England taking Scotland and Ireland, culminating in Great Britain, and France taking over around a dozen smaller quasi-independent duchies, counties, and whatnot - the most important ones being Bourgundy and Brittany. Finally culminating in ... well, France.
As a result of the friction which inevitably comes with centralization of power, at some point Britain decides to chop its king's head off around 1649 and become a republic for a bit. France eventually reaches a similar boiling point and does the same 140 years later with their own king.
There's some minor unimportant stuff going on in the meanwhile with trade, religion, and stuff like that, but it's just theming. Ultimately it's a classical "deuteragonist empires" story that continues until roughly the end of the 19th century, after which it all goes to shit for pretty much everyone.