So, as an attempt to summarise the replies somewhat.

We should:

-Treat all IXes as equal LocalPref wise
-Optional: prepend an AS once on routes learnt from AKL-IX so it matches path length with Citylink run IXes
-Do further ASPath length mangling if you wish to prefer one IX over another (but probably only vary the path by +/- 1 AS)

Vocus international customers should:

-Use an appropriate Community to achieve AS path prepending on their advertisements by Vocus to the various IXes so as to not attract domestic traffic in their international tubez.

Does that all seem sensible?

Cheers
Dave