I'm not sure what classes are available at HQ for foreigners on an occasional basis. If you are a Ki Society student, it would be best to make arrangements through your Chief Instructor. If not, you may wish to contact Ki No Kenkyukai directly with your questions. There is a World Camp in late October each year where classes are taught in English or translated. As far as I know, all other classes are taught in Japanese. If you like, I can check with Kashiwaya Sensei and see what he says about training at HQ. I will also see Shinichi Sensei who teaches there in June and would probably have a chance to ask about this as well.
Ki No Kenkyukai information email is
headoffice@ki-society.comand you can see the English website for Ki no Kenkyukai by clicking
HERE.