Are there any video recodings of them? I would love to see Grobnok or agincourt.

I don't know about any video recordings of reenactments...but, depending on where you are, you might want to check with a nearby SCA (Society for Creative Anachronism) or ECS (Empire of Chivalry and Steel) group. Many of the members of those organizations are also involved in other reenactments, or at least can put you in touch with someone who is.

In fact, if you have a good hand with a video camera, you may get more reenactment footage than you know what to do with. I've seen videographers at a few SCA "wars", and ESPN has even aired the occasional event on late-night programming.