Hi Suzie
Not sure about aerators, but we had a similar problem and were advised by a friend (horticulturist) to dig drainage pits into the lawn. This involved digging three big holes about 2m square and 4m deep and filling them with gravel then replacing over the lawn. Hard work but it seems to have done the trick!
Our soil was heavily compact for at least the top two metres and my understanding is that you have to get down beneath that to help the problem. I'm not really clued in on aerators though - sorry. Hope you solve the problem.
W