Well I practice under Sensei William's organisation, the Ki Federation of Great Britain and on occasion under Sensei Williams himself. As you will probably know Sensei K Williams took over The Hut when Abbe SEnsei left to teach the Japanese Olympic Judo team.
SEnsei Williams's style has also been heavily influenced by Tohei Sensei and as such I practice what I would consider a 'soft' style. Not that it means its any easier, but the idea of non resistance is more centrally taught than the Aikikai style that I also practice.
I find the main difference is that more 'martial' aspects of AIkido are brought out in the Aikikai, like strong atemi, breaking balance, dead zones and the like. In Ki Aikido, these ideas are brought together through the idea of being light and extending Ki, which seems to me to have the same result.
Magus, where do you practice in Reading? I train with the Ki Federation on Elm Road and the Aikikai on the Reading Uni Campus.....