Although I'm not sure whether Aikido rode on the back of Judo in the UK (it is still quite hard to find Aikido classes in some areas); it seems to be one of those martial arts you only hear of when you practise another martial art such as Judo or Karate.
Chiba Sensei was sent to England at the request of some Judo organisation who were to sponsor him, but they changed their mind just before he came and he had to get a private sponsor or something. I read it in an interview on aikidofaq
Here in Ireland I never heard of Aikido. (I thought Seagal did just Karate..) A friend dragged me along to a class one night about two years ago. Recently, though, I've seen it on an ad for a building society here, and in a fairly rubbish Irish sitcom too. So there you go.