It appears that Google has begun to trial a type of re-marketing where it uses previously searched for locations to display adverts for subsequent generic searches.
For example, a search for 'holidays in Barbados' followed by a generic search for just 'holidays' results in ads being displayed specific to the location of the previous search.
In the screen shots below, you can see the change in the results pages for the generic search 'hotels' after a search for 'hotels in Blackpool'.
Search 1: 'hotels' results (as expected)
Search 2: 'hotels in Blackpool' (as expected)
Search 3: 'hotels' (now showing Blackpool adverts)
This illustrates that Google is re-marketing the PPC adverts to previous searches. Interestingly, these results are not due to being signed in to a Google account.