I tried importing directly using the iam, but it didn't appear properly with the surfaces. At the moment I am just trying to use IGES files, which preserves the structure, but doesn't preserve the colours, and then adding the colours later.
By "it didn't appear properly with the surfaces" do you mean like the image above where there are no materials applied or there are surfaces missing?
Because I think rather then going iges and then having to recreate all the materials it might be easier to go iam and then just manually apply the materials that are already created.
The .iam will have all the structure. In fact it may have too much but you can cull out the unnecessary bits.
"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675