Since I did the original tests with Varicam it was clear that there was a problem somewhere, the blacks just weren't right.
Thanks to help from Nick Shaw we have tracked this down to full or extended levels being wrongly identified as legal levels.
If Resolve is used in its normal auto mode it will select the wrong data range as a result of this faulty info.
This sequence has been rendered out after manually setting all clips to Data levels in the media section of Resolve, I have then used ACES V1 and the Varicam IDT with standard RRT and rec 709 ODT matching the levels of the middle grey patch with gain adjustments only and setting the contrast on all clips to 0.75.
Finally we have the full dynamic range that the Varicam is capable of!!