Chelsea have reached an agreement with Aston Villa for the permanent transfer of Carney Chukwuemeka for a fee in the region of £20m.   The 18-year-old has been given permission to travel to London to discuss personal terms and undergo a medical to complete the transfer process.   The Aston Villa midfielder is set to join Chelsea after six years at Villa Park; 18-year-old had 12 months remaining on his contract and had no interest in signing an extension; the England U19 international was part of the squad that lifted the U19 Euros this summer.   Barcelona had