There's only one style used.
In most games released in the UK, you still have US english, although in some games they actually change it, in most they don't bother, it's still english.
Also, you say it's easier for you to read spanish than portugal's portuguese? Now that's really decadent, I have several brasilian friends and all of them can read and understand it just fine, it's the same friggin language, just a few words change.
Anyway, when a game is translated, they mainly use the European counterparts (for multi-language), mainly since it's like the origin so to say, for spanish you have Spain's and not Mexico's or Argentina's (yeah, they're different) and in the rare chance a game is translated in portuguese, it's translated in european Portuguese, since the localisation is meant for Europe, not elsewhere.
Point is, Australia doesn't get a localisation in their english, it uses the same english an European copy does, if the game in the UK uses american english, then they get american english, if it uses british, then they get british, it works like that. Simple, right? :3
pyromaniac is right on this one, so you shouldn't argue when you're on the wrong. z.z
