I love this thread
Even more so than cars and fish (aquarium), coffee is my passion. (Random fact for ya)
As Joe said, if you can find a "decent" cafe in Perth, stick to it! Also as Joe said, intrinsically, an espresso shot should be slightly sweet (more so with a 100% Arabica bean) and should be strong and intense, but not bitter. If your espresso (or however you prefer to drink coffee) has significantly bitter undertones, it is generally because the dose has been over-extracted.
I dont often drink flat whites, but when I do, I order it as a doppio ristretto flat white. Basically, ristretto is a short pour, or only the first 15-20seconds of a standard pour. And doppio simply means double in Italian. Meaning the doppio ristretto flat white should still be made of a 30ml shot, however it's 2x15ml short pours. I find this way, if Im somewhere where i dont know the quality of their coffee's, I generally get something that is at least drinkable.