Just watched an episode on yesterday - all about the Welsh rebellion against King Henry IV. Learned loads about this period and its inspired me to definitely look into developing a medieval army.
The battles look interesting - only a few thousand each side, billmen, men-at-arms and knights fighting on foot etc. And of course the devastating Welsh longbow.
Probably a project for the second half of the year (after the Prussians and British are finished - and the Greeks, Gauls and Parthians...).