Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Adelaide to Belfast as you normally would.
Adelaide (ADL) is the airport you will fly out of if you book a flight from Adelaide to Belfast. You should not have trouble finding flights to Belfast from Adelaide; the airport handles an average of 0 outbound flights to Belfast per day. You should also have plenty of airline options to choose from since 1 airline has flights from the Adelaide airport to Belfast. It is only a 6.6 km journey to Adelaide (ADL) from Adelaide’s city centre.