Re: British Seminars ?
There are three Aikido Summer Camps that I know of near you hosting the following 6th dan (hombu registered) and above teachers:
BAF, Chester - Senseis Kanetska, Cottier, Holland and Kobyashi.
UKA, Shropshire - Senseis Sugawra, Smith, Smith, Jones, Brady, Haywood.
BA, Bangor, N Wales - Senseis Chiba, Miyamoto, Chen, Cassells, Mooney.
I know the first two are very good and the third comes highly recomended. Hell, go to all three!
There is a dojo run by sensei Dave Yates in Manchester that you might wan to have a look at.