Large! The thing that gets me is that, geographically, all of the UK would fit easily into the state of Oregon, but you'd have to be a linguist to describe even one distinctly Oregonian accent, let alone dozens. It's not surprising to me that a very old country would have so many accents, but it's surprising that they would still perpetuate into the present, after mass media, travel, and mass communication seems to have flattened or homogenized so many fine distinctions based on geographic isolation.