The pilot of VH-LQA was conducting a practice ILS approach for runway 23 at Adelaide Airport. Approaching the localizer (LLZ) at 3000ft air traffic control (ATC) instructed him to enter a holding pattern between 28 and 34km north east of Adelaide to maintain horizontal separation standards with VH-YMJ, which had been cleared by ATC to intercept the 23 LLZ at 3000ft, from the east, for its arrival to Adelaide. After completion of the holding pattern, and not having received any further instructions from ATC, the pilot of VH-LQA believed he could continue the practice ILS without any further clearance and intercepted the LLZ. He was instructed three times in quick succession to turn right onto a heading of 310 degrees, and the pilot of VH-YMJ was instructed to continue turning left. The two aircraft passed at the same height with less than 5km horizontal separation.