Many are probably already aware of this excellent Scottish resource:
http://www.ambaile.org.uk/en/page/show_home_page.html
Visited just now to grab the Far North branch line track plans and gradient profiles and note they now allow you to download the actual images rather than just viewing on line. Many thanks to the site curator for allowing this as the reference material can now be preserved locally and in the long term saves them bandwidth, keep popping on the site to check things.
So dare I say... Lybster here we come!