I have to confess that I just sat down and enjoyed it. Giant Cyber-robot ("Hmm, that's a bit silly, but never mind") and liked the rest of it. You're right about the robot, though. Mind you, the Cybermen actually have a long history of being illogic and allergic to improbable things.

The only thing I had a problem was with 1851 being a boring year, but I thought the Doctor might be being ironic.