You're welcome Joe.
Regarding those links that you mention; they could potentially cause an issue such as link spamming, which can happen when two websites send each other a lot of reciprocal links.
(Simpler solution towards the end) ~ My advice would be to remove them and make it clear on the website that those on the UK site, in the US, can visit the US site and vice versa.
As some landing pages will no doubt be deep pages (i.e. not the homepage) perhaps a widget type of box in a prominent position would help to direct visitors to the other site if they are on the wrong site at the time. EG. "If you're a visitor from the US then visit our site especially for our US customers" or such like.
With some clever coding (and use of nofollow for such links) you could get it to work that when clicked on, the visitor goes to the corresponding page on the other site.
Or alternatively, an easier solution, make sure that all those links are "nofollow" links so that search spiders don't follow them, reducing the risk of a penalty.
Regards
Simon
