Westpac is uses https://ausiex.com.au/ but I'd find it hard to...

Westpac is uses https://ausiex.com.au/ but I'd find it hard to believe that's all westpac retail buying.

As a Westpac Share Trading client your shares will be broker sponsored
by the Australian Investment Exchange (AUSIEX) on the CHESS subregister. You will receive a paper statement for each
company shareholding confirming your registered details and the number of shares you own regardless of whether
the shares are Issuer sponsored or Broker sponsored.