Considering we didn't get the Avensis in Aus (the Avensis Verso is a different animal) I highly doubt it has been looked at much here. Also I believe all Aus-delivered ZZT231s had 275mm front brakes (that guide refers to 255mm which is probably the overseas 1ZZ povo-spec).
As an aside, do you know which part of your current setup is letting you down? If it's the calipers, maybe check out if the twin-piston AE101/AE111 SuperStrut calipers can be made to fit? I'm using an ST204 pad carrier to adapt them to my AE102 MacPherson strut (the SuperStrut hubs are much bigger) so I can retain the 275mm disc diameter.
Ahh.... right. Thanks so much for your reply, sounds like the Avensis brakes are not an option.
It's not so much the braking performance which is letting us down, more the reliability and feel. After the brakes start to heat up the pedal gets pretty spongy and putting the boot in doesn't fill you with confidence.
We are also experiencing some fairly bad wear in the EBC yellowstuff pads; inside pad is just about on the backing plate at the 2 hour mark. I suspect this is due to too much heat and issues with the pins on the calipers (bent or float in the carrier). We are running dot 5.1 brake fluid and I have some new braided lines and calipers to put on. Fingers crossed they help! If it continues to become an issue, I'll look further into your alternative ideas. Thanks again, I really appreciate it.