The best betting sites (for withdrawals) process withdrawal payments multiple times a day, and with Osko or NPP. With these services, the money will normally go through instantly (maybe slower if it's a first deposit to a new account, or if it is a large amount).
The issue with bookmakers, is getting them to find the time to process withdrawals. Ideally, there'd be someone sitting there processing them instantly, but life is not that good. Nearly all bookmakers will have a set time that they process withdrawals, and usually it is daily. The bookmakers will choose a cut-off time, and from there they will process everyone who has requested a withdrawal prior to that time. So, the later in the day the cut-off time is, the better they are for withdrawals.
Is my bank with Osko?
Most likely. Around 50 banks in Australia offer real time payments via Osko, including the big 4 (ANZ, CommBank, NAB & Westpac).