I suppose it depends on your definitions of "castle", but surely Baynard's Castle must count? (There's not much left of it, but then the same can be said of the one in Ruislip).
Caesars Camp on Wimbledon Common? (Actually misnamed, as it is Iron Age)
Does Jack Straw's Castle count?
One would not expect to find a Norman castle in the Domesday Book, which was essentially a stocktaking exercise of the assets seized/inherited by William the Conquerer in 1066. And certainly anything built in Middlesex in the 9th century wouldn't be Norman - it was part of the Kingdom of Mercia at the time.
Kingston has a "Castle Street" but there is no castle - the street is apparently named after a Mr Castle. It also has a housing development on a former barracks (of which the gatehouse remains), called The Keep.