In some cases, I had heard of the bands, but just hadn't heard any of their music. In other cases, I had heard their music.
In reading through the comments, it seems to me quite a few people missed the point. This is a list of bands that might have been popular in the UK, but not the U.S. Some people commenting seemed offended some of their favorite bands weren't on the list. This is not a popularity list. It's a list of bands from the UK relatively unknown in America. Also, it doesn't mean all Americans haven't heard of these bands. In my case, for example, I had heard a lot of music by Stereophonics, but just thought it was way too pop and not rock enough at all. Some of those other bands might be more to my liking if I listen enough to some of their music. Kasabian would be prime example. I've heard a lot about them, but wouldn't be able to name even one song by them. In general, I'm not too familiar with this time period in music, whether American, British or something else. But I'm always interested in something new if I can just find it. Just because a band wasn't popular in America isn't a determining factor to me. I'm interested in what I think myself.