Depends who the shop is as to how easy it will be, if it was one of the Dixons Group then good luck! If you are thinking of sending back to manufacturer or warranty provider, then read the warranty paperwork to see what your options are for exchange/refund as these will vary, sometimes willbe good and sometimes rubbish.
Any legal rights you have are only between you and the shop, so if you go back to them, as repairs haven't worked you have got a stronger case for exchange/refund.
Just bear in mind that you have different rights under guarantee/warranty against manufacturer and legal rights against the shop.