Even when only one in the circuit and you receive a call you need to know and hopefully see visually where any other aircraft is. I was established on downwind at an airfield to the west of Townsville about half way along downwind and an aircraft called downwind. (I had called my inbound and joining downwind.) I could not see this aircraft so asked height and asked my wife to look for it also. They responded same height, so I did then not want to move any direction or height other than my current track. They could not see me. Then a short time later saw them ahead at same level, crossing ahead from stb to port. They were actually in the base area then turned port down the dead side and later actually joined their downwind. Flying school aircraft. Didn't waste any time discussing matter as history of not being receptive to discussions. Poor attitude of white shirt and epaulets etc. Just poor circuit join and wrong call on their part. Certainly, had us looking for them considering their call was that they were where we were. My mind picture was of a collision one on top of other.