Hello,
I don't think this to be the issue.
Why? Because yesterday as a final last-ditch attempt to get this done, I tried converting the SBS 2008 box to a "Vmware Workstation Machine", and targetted a simple CIFS share on a workstation that I had handy with a 500GB SATA drive direclty attached to the motherboard, and the speed was approximately 50-55 MB/s.
The problem is within the converter. Just wondering where else I could have checked. I've already wasted far too much time on this as it is, if I can't figure it out I'm going to have to go the "VMWare workstation machine" and then uploading to to the datastore using winSCP or similar.