Over the past week or so, I have been hearing chatter about a Google UK search shuffle of some kind. I did not see any forum threads in the discussion forums I track, until Gabs posted one in Search Engine Roundtable Forums.
The changed pushed many sites a couple hundred points down in the Google UK search results. But as of yesterday, many of those sites returned to their previous position.
Last week many seo noticed an influx of US domain for many terms in the uk effecting rankings..
Many UK ranking seem to of returned today.. Hope it sticks...
You can see some of the tweets on uk serps discussing the findings.
Forum discussion at Search Engine Roundtable Forums.