That would be south south west.
London is in the south east of England. The 'south north' does not exist - it doesn't make sense.
No Europe is northeast of South America.
Wind direction is the direction from which the wind originates. A northern wind blows south, it originates in the north. See the related link for more information.
"South by South by South" is the clue to the direction of Thorn Valley in The Secret of N.I.M.H. 2: Timmy to the Rescue.