Here is a thread with mechanical workshops in Perth, have you called them all to see if they are open on a Saturday? I know some will be open but not strictly advertise the fact
http://www.perth-wrx.com/vb/mechanicals/6775-perth-workshops.html
Here is an old performance thread. We'll be starting a new, better one soon but you'll be able to flick through some peoples results
http://www.perth-wrx.com/vb/mechanicals/10658-horsepower-how-much-you-got.html
Personally I don't know of any workshops in Funbury, I think sicem wrex racing in mandurah would be your closest, but i have no experince of them either
Give Bart from South West Brakes a call, he might have a better idea