tedster - 2:04 am on May 8, 2012 (gmt 0)
Yes, I have seen this kind of behavior especially when the rankings are on page two or further. I think it has something to do with Google's statistical and machine learning (best guess for now.) In fact, I've also seen in from the US, not only the UK.
For me there's nothing to be done except to continue to create and market superb content, and serve visitors to the nth degree. Chasing visitors IS the new SEO for Google, IMO.