A Cre8asite Forum thread reports that for some Google searchers in the UK, Google was unreachable for a short period of time. eKstreme summarizes many of the issues noticed. Some people were unable to reach Gmail, Google.com and many other Google services.
If you look at a search at Summarize for google down, you will see many people talking about Google going down.
I scanned the other forums and did not see any mentions of Google going down in the UK.
My assumption is that a major UK ISP had issues and it impacted reaching Google. I doubt Google, itself, was down. But rather, what is more likely, is that the ISP had connectivity issues to certain web sites.
Forum discussion at Cre8asite Forum.