(Reuters) - South Africa is mulling retaliatory measures to protect its centuries-old wine industry and counter job losses caused by a British retailers' move to buy the product in bulk rather than in bottles, a trade official said. British retailers including Tesco and J Sainsbury are bottling the bulk wine themselves, leading so far to as many as 700 job losses in South Africa, said Stephen Hanival, chief director of agro-processing at the Department of Trade and Industry.