LONDON  - World oil prices continued to slide on Friday, despite upbeat non-farm payrolls data in the United States, as the market was dogged by worries over weak global demand, dealers said. Brent North Sea crude for delivery in November retreated 78 cents to $111.80 a barrel in late afternoon trade in London. New York's main contract, West Texas Intermediate (WTI) or light sweet crude for November, dipped $1.40 to $90.31 a barrel.