Yes, you (and I) have just missed them, they were in London Oct 27th.
Their movements are detailed on their website. If you send them an email they will notify you the next time they have a visit planned. I have been trying to make it down to see them for a while now.
Thanks! It looks like they come twice a year or so? Damn... that's a long wait! Is there a thread that lists some of their indicative prices? I've searched but haven't found it.