Thank you for the responses, and my commiserations to those who have found themselves in a similar situation. I have today received a response from Air Services advising that they have undergone a significant change in program resulting in a reduction in the number of spots for the ATC traineeship program hence the reassessment against their key selection criteria - which they refer to as a 're-calibration process'. They are otherwise not in a position to provide any individual feedback in regards to which aspect of my assessments to date resulted in my 're-calibrated' results making my application now unsuccessful. They have 'understood' my disappointment, thanked me for my understanding and patience ,and strongly encouraged me to apply in the near future, with the next intake anticipated in late 2017.
I agree with previous posters that I have no issue with Air Services setting or raising the bar, but it is how they handled the issue in these circumstances where they had previously advised applicants that they had advanced in the recruitment process, to do an about face some 10 months later, due to their own internal operational issues (and arguably poor management).
I agree with LFVA's views that is is in bad taste, and reflects poorly on a prospective employer to treat people as discardable and replaceable in the circumstances that they have.
Overall though, I am happy to have received this insight into the organisation at this stage, rather than progressing to a traineeship or further and then discovering their standards and operating procedures.
Thank you again to all that have contributed to this thread, and also provided recent insight and commiserations in regards to be treated in a similar manner.
From a personal perspective I don't anticipate reapplying or otherwise pursuing any form of employment with Air Services in the foreseeable future.