As Drillsearch is an off market bid, the shareholders who...

As Drillsearch is an off market bid, the shareholders who accepted are allowed to accept offer outside the ASX market. No requirement to wait for a higher offer or to look after other shareholders. Unconditional offers are difficult to reversed under Contract Law. There is no cooling off period. Takeover panel cannot do much IMO in this situation.
with NSE, their intention is to sell down their PEL570 52% interest. That would be the next bidding round. AQO likely have preemptive rights to match any offer NSE receives. Good result for everyone.