I just wanted to share a couple of URLs that give access to some very interesting GC siganalling diagrams. However, please note that most (but not quite all) show post-1923 amendments and so must be used with care when GC era arrangements are what you want.
LNER Signal Box Diagrams As you might guess from the title this site is not just about the GC. But it does have an extensive selection of GC section diagrams and some from the joint lines.
Lymm Observatory Another exceedingly useful collection. Again, not just the GC, although for the GC there is a particular focus on Woodhead and the adjoining lines.
For anyone wishing to make models there is an excellent thread on RMWeb. Suffice it to say that the OP, Jon Fitness, has probably forgotten more about making signals than I shall ever know. He works in 7mm scale but the principles apply to all scales.