235's will be fine on a 7.5" rim. You might notice slightly more wear in the centre if anything. If you think about it, compared to an 8" rim, there is only 1/4" or 6.35mm each side. You will get more variation than that from one brand of tire to another even though they are all designated as 235mm.
make sure you get wheels to suit an AU. not an EL i've been told that it will really affect the handling of your car
That would have to be an understatement XR8MICK. EL wheels on an AU would probably poke outside the bodywork the offset is considerably different.