This is still very much a work in progress but I thought it might help as some sort of starting point. I'm open to any alternate ways of doing this.
Basically I have a BT which will make my AI (a spider) walk around randomly and detect for a certain enemy. If one is found it will persue the enemy using steering and then attack.
@siflandolly I have been meaning to thank you for this post, I know it has been a great help. Would you mind if I posted it on the Unity Forums? Or would you like to do that?
Sure, feel free to post on the Unity Forums. I'm still working on these files and will keep updating the Evernote but at least it might give some people something to start with.