DickyPearse
This might answer your question.
I applied for a dispensation to conduct a straight in approach of less than five miles when it is safer to do so.
Its interesting to note that CASA's response cites safety in helping to separate aircraft in the traffic area.
Such an approach would reduce the opportunity for all pilots in the area to make a comprehensive assessment of the traffic and achieve appropriate separation and to enable the pilot flying the straight-in approach to give way to aircraft flying a standard circuit.
I have seen no such evidence both here and in the United States. Surely too then they would be open to increasing the safety levels by allowing a join on base leg inside 5nm on those occasions safety warrants it.