I can't recall exactly how many ATOL exams you will have to do, but I can ask a former RAF Herk mate for his experiences.
You may also have to do a MECIR practise and flight test (and IREX theory), and apply for an ASIC (security pass).
CASA have also invented a new MCC rating too - which off course won't recognise your Multi-Crew experience in those blasted British flying machines...
Feel free to PM me.