<br /><br />Can't answer your 1st point but the reason they recruit British officers is 3 fold. <br />1 we use similar laws being members of the commonwealth<br />2 we speak English as default<br />3 we used to be the best police officers in the world and that opinion hasn't shifted yet despite Mrs May & Mr Windsor's best efforts
Well English is the only real reason. Australia has been accepting experienced immigrants to all sorts of jobs for years because it's a growing country with lots of space, and lots of room for growth. That comes with demands on services that you can't fill just by hiring locals - even if the locals wanted the jobs. You can't magically expand a police force overnight, and especially expand the number of experienced officers - if you want lots more cops with 5+ years service you either wait 5 years or import them. This is doubly true for niche roles - it's much easier to hire an experienced detective than it is to grow one. That experienced officer can then also pass on their experience.
The Australian armed forces are the same in hiring Brits, especially for specialist roles. New Zealand does the same. The Canadian police were doing it for years, especially in Alberta when the oil boom really kicked off, because they needed lots of experienced cops quickly.
Mining is the reason many of the locals don't want to work for the police - if its physical outside labour you want to do then you earn far more in the mines than you do the police.