Atomic Rooster was in interesting band. They were certainly British, and very eclectic. There are also connexions with other bands (some of which I have covered here) and with other, less well known ones.
This band came to be in much part between the collaboration betwixt the folks producing The Crazy World of Arthur Brown and several other bands, including The Who. Their connexions include King Crimson, Emerson, Lake, and Palmer, and a couple of other bands that I would rather folks mention in the comments. Shall we see more about them?