Sunday Funday! - Total War: Warhammer Custom Battle - Valiant Defeat!

So I decided to record and upload a custom battle I set up in Total War: Warhammer as something fun for Sunday that differs from my usual written articles. I have played this battle a few times and just cant seem to pull off the win. I am still quite fresh to the game so any advice would be great. The first few times I attempted this battle I had a lot more low cost troops and it was a disaster. My Bretonnian allies seem to go all out attack while I prefer to sit back and defend. I am thinking perhaps I should set out to attack with them so they do not get isolated? Anyway watch below as chaos ensues!

The current set up of my army (as seen in the video) is as follows. I fail in the battle to prevent the enemy masses breaking through to my archers and artillery. I clearly state at the set up stage that im going to put my best troops at my centre and then stick them on the right flank! My feeling is that I need something to counter the enemy creatures and heavy units. So i'm going to experiment with my set up until I pull off the win. My other option is to join the allied assault and attempt to break the enemy on mass!

Karl Franz on a Warhorse
5 x Swordsman
1 x Halberdiers
2 x Greatswords
4 x Crossbow
1 x Reiksguard
2 x Helstorm Rocket Battery