I'm pretty happy with the black and white result.
Now I'm going through the gradual process of shading and colouring it.
I'm not so happy with the way this is going, I'm just experimenting with a few techniques until I get something I like.
Since I'm having trouble responding to a query from Johnn Four on the previous post, I'll answer it here before I move on to other things. Most of my mapping is done on plain photocopy paper, first in pencil then inked with a range of fine tipped markers (0.1, 0.3, 0.5 and 0.7mm tips). Photocopy paper generally works pretty well over the monitor as a tracing sheet if you're in a dark room, proper drawing film or tracing paper is more transparent (as opposed to the copy paper which is translucent until these conditions), and allows for more detail. If you're interested in my general mapping style and techniques, there's a pretty comprehensive tutorial (with a link at the top of this blog).
I could end up working on the colouring of this map for days, so I won't bore you with details of how I used this layer in that fashion, and applied which filter where. This tutorial is about world building, not map colouring. I may show some progress images scattered between other posts in this series if people are interested.