I found a way to do it better than just general scaling.
Diptrace can export the holes part of the file as a DXF so I did that.
The vertical and horizontal measurements (on my actual board) were out of scale by slightly different amounts so I needed to scale them independently. Brought the DXF into a cad program then scaled X and Y axis independantly and now have a hole drilling drawing of the perfect dimensions.
Import the new DXF into my cam software and good to go.
Keith.