Thank you very much for you replies Fligh% and Originalsurfmax.
I have finally had some success in importing my files.
The best way to get it in seemed to be scaling all the geometry down to .001 as you suggested Originalsurfmax, moving everything near to the origin, changing the dwg file limits(LIMMAX) to the minimum to cover the geometry and then saving as a release 14 dxf format. It came in very cleanly into Blender.
The 3ds export from CAD did not help me as it only works for solids and surfaces, but not for lines. The other alternative that seemed to work was to open up the dxf in ‘Crossroads’ and convert it into a 3ds file. That somehow changed the lines into a mesh object. The import was a bit messy with many duplicated vertices though. The other method worked better for my geometry.
Thanks again for your quick responses.