Cameron's 'Brexit' riddle: Row with EU or row with Eurosceptics?

By William James and Guy Faulconbridge LONDON (Reuters) - When David Cameron urges European Union leaders on Thursday to do a deal to keep Britain in the bloc, he will face a riddle that has haunted Conservative prime ministers for three decades: a row with Europe or a row with Eurosceptics at home? Cameron's bid to renegotiate the terms of Britain's membership of the bloc ahead of a referendum he has promised by the end of 2017, has hit the rocks over a demand to make working EU migrants wait f