Great advice Watchman, finally some more formations to play with. Another even better consequence of this is that night battles now work in my campaign... nice.

I first linked the BI.exe to the copied data folder as you specified, but this caused a CTD after faction selection in my campaign. I then linked the exe to the original data folder directly '-mod:data' which seems to work fine for me.

Is there any way to get the custom battles working?

My thanks.