M_Bison - 9:55 am on Jul 31, 2008 (gmt 0)

Could this be because Wikipedia has enough inbound links from the UK that those suffice to include it in UK results?

No, I am seeing .com.au URLs in "Pages from UK" and .co.uk URLs in "Pages from Australia".

Something is definitely wrong, which isn't surprising since Google has had so many geo-targeting issues in the past.