Pre-populate field in content from user profile
Firstly, thanks to all for the help. I followed your advice and configured devel to print $page. Followed the structure of the page and came up with the amended the code:

$form['field_location']['und'][0]['country']['#value']


Leaving Devel enabled, I can see the value has been set correctly to gb. However, this breaks the google map functionality.

On to the next problem :)