I have had a box of the Fireforge lying around and had only built one sprue of them, so had about 30 spare models.
There are some helmets in the Fireforge set that look similar to the Perry Agincourt figures and some bodies in quilted akerton jackets. I think you could use about half of the models in an English army and probably the rest could be mixed into the French army as city militia if you changed the shields to pavise shapes.
I am currently doing some simple conversions of Fireforge Foot to supplement my Perry Agincourt English archers. I have used some spare Perry arms (axe and trumpet) on the Fireforge models. I have converted two of the Fireforge spearmen with longer spears so that they can have St George flags. So far, I have two flag bearers and two trumpeters and one axeman. I plan to do a few more with hand weapons for melee and maybe a few as working teams planting stakes.