Hello,
Google should be able to geo-locate the site automatically by looking at citations and information contained within your website so I don't really worry too much about using the geo targetting setting in Webmaster tools.
What I would suggest that as well as building links to this site, make sure you do lots of citations too as some of the terms you are targeting, including 'london tours'' brings up local results on both Google.com and Google.co.uk.
Also, if you do a search for dga tours on google.co.uk it thinks the site is located in the USA.
If I were you I'd put the whole company address on the clients website, I would also build some citations so you can also get a local, or combined local / organic, result on the search engine results page - they should also give you rankings a boost too.
Hope this helps.
Gordon
