(Warning Big Images)
I have made it a bit easier:
Locate your Warband folder and extract the mountblade warband folder to the folder that contains the mountblade warband folder.
-If you have BR_Pants already thats because it was Brunswickers (If you replace won't do anything different, it's just for those that didn't have the texture)
-Yes, British_hats must be replaced. (make a back up of your folder)
-Replace any dutch_....dds files you have. (There are two, Dutch_shakos and Dutch_shakos2, I will mix em up later)
-Line Infantry Replaces Coldstream Guards
-Artillery Replaces Royal Artillery