Hello! The next update will include more information on the signals and signs, but only in text. I do agree that pictures of the signals would be more helpful, and will consider them for the second or third update.
Granted, the graphics are not very well thought out because I'm still learning things and wanted to focus on the physics and overall feel. Some of the future updates will bring improvements in this regard. There's also plenty of opportunities for optimisation in the graphics but also in other areas of the program. The seat material is shared with several other cab objects, so separating it would probably not help.
In the modern railway there certainly are advance warnings to speed restrictions, but 1960's Britain, I'm not so sure. I'd be interested in knowing more about this from a reliable source. Maybe the drivers just had to rely on their memory and knowledge of the route. The limit signs were originally painted white, but being hard to spot in snow, were later converted to yellow. They currently don't stand out very well, I agree, maybe adjusting the overall illumination to a more realistic direction would help.
In the next update you can move around in the cab and stick your head through the side windows, so that'll help spotting the signals in tight corners.
Thanks for your suggestions!