Research fascinates me. Right now I'm thinking myself back into the sixteenth century and it's a wonderful opportunity to hunt down obscure names and places on the internet.
Many things have to be considered. By the fifteenth century cannon had improved, but they were still inaccurate and unreliable, as likely to explode and kill their 'handlers' as the enemy. They were unwieldly and could not be fired more than perhaps seven times a day because they grew too hot. Handguns were in use, but longbowmen, foot soldiers with pikes and heavy cavalry units were still the ones who won the battles.
By the 1400s brick was the coming building material, and there are some splendid castles made of brick. By the time the Wars of the Roses were over, ideas filtering in from Italy affected the architecture of England. By Elizabeth's time, castle building was over. Some were altered and redesigned as stately homes.
Handguns became more efficient with the matchlock pistol towards the end of the fifteenth century. Renamed an arquebus, it had a short wooden butt designed to rest against the shoulder. Cannon became lighter, and thus more mobile. With these new tools, the old accepted methods of warfare had to change.
Some castles were inhabited, besieged, felled and restored well into the seventeenth century. Some are still used today as family homes, but others became prisons and storerooms. Yet others fell into disrepair and their stone was spirited away by those anxious to rebuild a fallen barn or delapidated farmhouse. For a period of three, perhaps four hundrd years, castles were the most important defensive building in a region. With Henry VIII, who changed so many things, castles morphed into stately homes, and forts and barracks were built to house soldiers. The last battle on English soil is generally accepted as the Battle of Sedgemoor in 1685, though Cumbria claims a skirmish involving a hundred dead as the English chased Bonnie Prince Charlie back over the border in 1745, and some claim the Falklands as 'English soil.'