Thank you for all your comments.

The ratio of the current map is the double page spread of a paperback, and I think they print in 200 dpi. No colour though after the cover, so have to play with greyscale. The original file was much darker and the forest stood out more, but I played with an adjustment layer of levels, to try and make it all a little more vivid, but I think i've lost some detail.

Thanks again for your thoughts, I'll post a few more variations soon and see what you all think.

T.B