Update...


Installed 3.4.1 on ZC 1.3.9d and it worked fine.
Uploaded the ozpost.php file for 3.5.0f and I lose the shipping estimator


On a clean 1.5.1, initially installed OZ 3.4.1, checked, all good. Uploaded the 3.5.0f ozpost.php file, removed and re-installed via Admin and Viola, all good..
Its returning rates via the shipping estimator and I can complete the order process.

Mike