Robert_Charlton - 2:06 am on Sep 19, 2012 (gmt 0)
For some reason my site is doing well in google.au Not bad - only half a world away! Why would I be getting traffic from Australia when my site is UK?
Jez123 - Back in May, 2012, we had some similar geo-confused results reported between Australia and US, and it may well be that Google is testing geo-intent. There's apparently an overlap of placenames, but some only show up when the search is more granular than just a search by the placename. Eg, some show up only with state modifiers (or whatever analogous regions are called in UK and Australia).
To check the details, look at my first post on the May 2012 update thread ( 5:45 pm on May 1, 2012 (PST -8) ), about the 31st post in the discussion, and read through until my "exchange" with web_speed ( 3:00 pm on May 2, 2012 (PST -8) ), msg#4448697....
Google Updates and SERP Changes - May 2012
The gist of it is that there are a bunch of town names that have either identical or very similar spellings, and I believe that some queries get modified by Google and/or sent to a different country because there are no local sites satisfying the query.
This seems to show up the most relatively soon after an update has rolled out. I think this may be Google "calibrating" the results, but that's a guess.
So, is there geo-intent related to your queries, or could there be? (Eg, ecommerce results might get localized simply because Google wants to return local results first).