Please close this thread, I have found the cause of my problem. It may be useful to others doing their first install of the Antec Kuhler H2O 920 though.
When you install the new cooler, make sure you go to the Bios and switch your CPU Fan setting to FULL. I had mine set on Auto and therefore it did not supply power to the fans at idle temps, thus although my fans were spinning at idle it must have been at less than 100rpm on some back ground voltage.
Once I changed the setting to full I had complete control over the coolooing system vis the dashboard desktop facility.