If according to WHMCS its a failure then account shall not create in the HC Panel as well is this what happening ?

Let me go through it tomorrow and I will give you a detailed answer on how each sceanrio plays out and how it should play out.
 
Thanks
Mark

In case anyone is wondering, I did go through and quite simply the WHMCS integration did not work. The HC.PHP file that is/was available from the HC website does not have the correct return codes for WHMCS to recognise that the result was successful or not.
 
If you search this forum you will find another post confirming this.