By Paul Sandle LONDON (Reuters) -Britain’s government said it will set out plans to sell Channel 4, the publicly owned but commercially funded broadcaster established in the 1980s, in a policy paper on Thursday. Channel 4 was created by Conservative Prime Minister Margaret Thatcher’s government to deliver an edgy alternative to the BBC and ITV, with a focus on under-served audiences. With no in-house production, it played a key role in establishing Britain’s independent programme making sector. The broadcaster’s management, lawmakers across parliament and television grandees oppose a sale, say…