Creating New Factions (not for VI)

I am not quite sure if this has been posted anywhere else. I do not have Viking Invasion so I guess - unless I am wrong - this hasn't been posted anywhere else in these forums.

Well I tried creating a new faction for M:TW - the Scottish. I edited the campmap/startpos txt files but on the first try it said it didn't recognise my new faction. The message came up like "No such faction SCOTTISH Column 28, Row 1". As the forums were down I didn't query this but put in the copied original files back in. I tried again and it almost worked except for the fact that the Campaign wouldn't work. The screen came up but you couldn't pick a period because of no available selection. I try again and again and this always happens.

So from the start, how can I make a new faction, eg the Scots, for Medieval : Total War (not for VI though)? Comments and links would be highly grateful for.