Hi Shells,
Thanks for the inputs! Interestingly yes we also have logged an SR for this issue

And the reply from Oracle is that Action Checks on Order Base Templates is not supported and is as per design. The problem that we had was that we have tried activating an Action Check of "ADD ORDER BASE". We have added an Allow Condition of the Saved Query of validating the Ship Unit Count to be non-zero or non-null.
When we try to add an Order Base using the Order Base Template, the Action Check "ADD ORDER BASE" does not get triggered and we have confirmed that by checking the glog.log file.
Oracle Support states that the default value for ship unit count when creating a new ShipUnit bean is '1', and there is not way to override in the code. Oracle have stated that this is the current design
But as my operations will have none of this, I have to explore other functions and hence I stumbled on USER EXIT.
As an update, interestingly I am getting some positive results from this functionality. I am currently testing this in my development server and will update you on my findings

Hopefully it will help you as well!
Cheers!
Ian