Preferably site.co.uk should reroute in an online search engine friendly way to site.com/uk as the need to all other nation-specific domains.
We do not recommend that websites reroute users from deep material such as site.com/uk/product.html as the user is likely to want to visit the real page they requested rather than being rerouted.
Web sites like FedEx offer a poor user experience as they require users to select their country as soon as they visit the homepage. Immediately choosing a nation based upon IP address would make the website much more effective.
Search engine optimization
Using a sub-folder rather than a sub-domain and even a different site indicates that any incoming links are going to help raise the total trust of the whole domain. Utilizing a various site for each nation or redirecting to sub-domains isnt going to make the most use of any incoming links.
It is important to bear in mind that Googlebot and other online search engine spiders are usually on a United States IP address. Unless your default setting is to send out US users to site.com you might require overriding the IP delivery policies for spiders. If the website was for a UK company however on a.com domain, you might be rerouting all United States users from site.com to site.com/us while keeping UK users on site.com. , if you reroute Google to the US sub-folder it can make it hard for Google to index your genuine homepage.