Gem_Hound is about to post. Here is some info for you and some questions.
1) you have a commander with your reserves: Who is he, and how does he react?
2) Your reserves have a few hundred on both flanks still alive- mostly so you can storify their end however you like. Do they kill someone attempting to surrendur? To they fake a surrendur? Fight to the death? Fall back for the Hills so they have the message? Up to you.
3) Your guards have flanked the Armoricans once again, between their new Phalanx and their archers: they cannot contact your normal folks, what do they do?
4) Your hill force does not know what is happening to your reserves until a messagner comes.