[vidarh]

In parts of England "should of" is in common use amongst younger speakers to the extent that "should of" to me is associated with South or East London more than non-native speakers (though it's in use many other places in England too).

See http://en.wikipedia.org/wiki/Dialect_levelling_in_Britain#Ex...

My four year old might occasionally use it because his friends does, and he knows it drives his mother absolutely crazy when she notices he uses South London dialect features.