Craig - looks like you are now becoming more aware of the potential minefield you are stepping into with painting up your Scots soldiers! Fear not - help is at hand from some of the worthies you are meeting on the forum - who will help you out when you get a bit confused ( just like they help me!). That book from Jim is a cracker - but unfortunately is out of print - and costs the proverbial arm & leg if you can find a used one.{eek3}
For me, my Simkin's illustrations provide a reasonably priced start - so glad you've ordered it - it's a wonderful read too - as the text is by the late (great) Bill Carman.
You will fid dates under each illustration - which helps stop you making mistakes, by having your soldiers painted as they were at different times in their history, when uniform details changed.
Another tip for you - input "Gordon Highlanders - Images" (to take just one example) into Google - and you will get dozens of pictures up. There will be a lot of dross, of course, but the occasional gem. I then use the "save as" function( right click on mouse) - and store the pics chosen in files for future use. I used to print off the ones I would use for painting - but now paint straight from the screen for details I require, (Saves paper and ink). Saving them into files stores them to bring up the pic at any time later. JUST USE FOR YOURSELF AS A PAINTING GUIDE though - as you may infringe copyright if you are tempted to use them for anything else.
Lastly - welcome again to painting your own, and look upon the research required as all part of the fun - and not a chore. It is great fun, finding out details - like the ones about differences in Battalion dress, as mentioned by Trooper.^&confuse
P.S make a start on your "Save as" files, by saving the contributions from Jim and Trooper - I have!!! - thanks both
Hope the above helps get you started ^&grin johnnybach