Thanks for the responses guys, I don't think I properly conveyed my issue in the original post.
There's no issue with the scale or the units in the actual design layers themselves. The drawings themselves are fine.
The situation is that we're trying to make a very small change to an annotation, basically just editing a dimension that is incorrect on a dwg file created by others.
The problem is that the dimensions are annotated in the equivalent to the Vectorworks sheet layer. Now Vectorworks sheet layers are always 1:1 (Unless some genius can tell me how to change this). When the file is imported to Vectorworks the dimensions now measure the space at 1:1.
So for example, I import a drawing which is drawn at 1:10. There's a dimension which is 380mm, when I go into the design layer, this is correct.
The actual dimension annotation however is drawn in the screen layer, and measures a space which is now at 1:1. So the annotation displays 38mm in Vectorworks instead of 380mm.
(Which is what is shown in the first screenshot above)
Hopefully this clarifies my query.