Just wanted to update the thread - I got the head up and running and fitted and its working fine. I need to spend some time now running some tests getting to grips with the settings to change contrast.
I've seen a few references (Paul Butzi) to using a system of combining the magenta and yellow dials to give variable contrast but constant exposure. I've got the article he wrote and the table of figures for durst heads (also quoted on the durst pro USA site) so intend to try them out at least.
Many thanks to all who have contributed to the knowledge I've gained over the last week or so!!