DXF attribute to z value

I have been trying to find a way of doing this for months. In the end, the only method I could find was to load the DXF into gvSIG and export it as a shapefile. Doing this adds the linestring z-value to the shapefile's DBF as an attribute.

In my case, the DXFs were OS OpenData containing contours, along with other data that I did not require, so I extracted just the contours to a new DXF before loading the file into gvSIG:

ogr2ogr -f DXF contours.dxf -where "LAYER='G8040201'" original.dxf

In FME you would want the 3DForcer transformer.