Just wondering how to fix cruise control on an AU3...

It turns on fine it just won't always set or go faster or slower.
I'm pretty sure its the buttons on the searing wheel.

Just wondering what to do now?

Fairly easy. If the usually work, then the switches are more likely to be at fault than the clockspring.
However - if they are all usually broken, or all usually working thats more indicative of a wiring problem (most likely with the clockspring)

If the switches are your problem, you can either replace the switch, or you can pull it apart and replace the microswitches. Ive bought them before on ebay from china and repaired the switches.
You can also purchase a replacement used switch on ebay, and if you have too much trouble finding them you should also be able to make an EF or EL right hand side switch work with some wiring changes.

If its the clockspring - same answer - off to ebay. Get a replacement one. You'll have to get an AU Clockspring only as the EF/EL ones do not have the right connector and are one conductor short.
Theyre not too hard to replace - just time and patience. Google, or search will be your friend

Nigel

As mentioned, if the switches are the problem, you can repair them. The little metal cover unclips, and you can remove the little metal disc, and clean with a cotton wool bud and metho.
From memory there can be a thin plastic covering, which you can replace with sticky tape.