I posted a search brief on this topic at Search Engine Land, when I saw Search Engine War noticing Google UK testing single line Sitelinks. But it seems like more folks in the UK are noticing the "classic" Sitelinks showing up. I call them "classic," because the first time we saw Sitelinks, they were in the form of a single line.
A WebmasterWorld thread has one UK searcher noticing them. They call it "mini" but there is nothing "mini" about having any extra line in the Google search results. Typically, Sitelinks look like this:
Eight links, in four rows and two columns. Earlier, Google was testing four links in a single column:
But originally, before we even knew what they were called, they were on a single line:
Search Engine War has a picture of the new "classic" Sitelinks in place.
Personally, I prefer the single line Sitelinks - at least from a searcher's perspective. Just seems cleaner and lets me see more results on a page.
Forum discussion at WebmasterWorld.