If you happen to be visiting London during Halloween, the London Eye will be hosting a Halloween theme event called “Witch Academy†from Oct. 24 through Halloween. The vent is designed for children and adults to learn spells, tricks and facts. Aside from the London Eye, the London Dungeon will also have a performance called Séance! from Oct. 1 to Nov. 1.
Halloween isn't as big as in the states but it's celebrated and many events are organized like fun races through the Royal Park or Hyde Park. Look for "haunted London," or "Jack the Ripper" tours.