Hi Duncan,
You're more than welcome to come by any chance you get. We're yoshinkan, but currently on the mat there are two who also study (or have studied) Aikikai. A guy who trained with us for 6 weeks during a visit to Japan was Tomiki, so we're pretty open about having other styles visit.
http://www.roppongi-yoshinkan.com
On the touristy side of things make sure you schedule a visit to the tsukiji fish market really early in the morning. In june, Hakone is also very nice and somewhat interesting.
cheers,
--Michael