My real problem came with choosing the colours and these are still not anywhere near right I think. I tried Color Brewer, but in the end I lifted the colours from an old shaded relief map of a part of the Alps I found on the Internet.
The rendering was done with MICRODEM and exported as a WGS84 JPG with a world file that I projected to an OSGB36 geotiff using gdalwarp.
Any comments on the colours, or anything else, would be welcomed. The terrain in this part of the world isn't dramatic, but it is important.