Factual error: It is barely credible that a young Victorian woman like Elena would even think about wearing a goatskin miniskirt - exposing her legs in those days would be akin to walking about topless nowadays. Even if she did those bright yellow cotton knickers - gleefully visible in the scene in the beehive - are in no way from the 1860s. Her pants are a hundred years ahead of their time.
Continuity mistake: The shots are badly mismatched when Demetrius saves the elderly slave about to fall from the rope. Their arms and legs shift positions multiple times between takes.
Factual error: With the radiation belt on fire, the icecaps begin to melt. The Seaview is bombarded by huge chucks of ice. The ice is sinking to the bottom like stones. Ice floats, it doesn't sink.
Other mistake: When the parent monster is just about to enter Piccadilly square, for a brief moment a view of a bus is shown. The writing on the bus is reversed.