As far as I can remember, Aer Lingus class of 1975 were the last class taught by the IAC, the training moved to Oxford, and then to Miami. I belive the reason was that the aircrafts were considerd unsuitable, there was also an issue over days lost due to low-visiblity, less in oxford, virtually nil in Miami. Aer Lingus had not recuited non pilots to train for some years before this.
Pilots from other military organisations were trained by the IAC, but , as far as I can remember this was carried out mainly at Bal'. I think the Nigerian Air Force were one of the customers.