A WebmasterWorld thread discusses, what they suggest to be, issues unique to UK based sites, within the UK only Google search results. One such example;
A site:domainname search lists the pages in the site ok when performed in the default search, but lists all pages APART from the homepage when done with the 'pages from the UK' option. Also, a search for the domain name shows the homepage in the #1 slot in a default search, but a search for the domain name using the 'pages from the UK' option shows the same list, but no homepage anywhere.
The site is hosted in the UK on a shared IP, physically located in the UK. I have located other .coms on the same IP and their homepages show up fine when the domain name is searched for using the 'pages from the UK' option.
Can this be related to last week's Google update (not specific to the UK only)? I think it may.
Forum discussion at WebmasterWorld.