High end CD player faulty twice during warranty period

I bought a high end cd player in December 2009 and returned it to the retailer after 4 weeks when the loading drawer failed to work properly. It was returned 4 weeks later having been repaired by the manufacturer. Fifteen months later (17 months into the 2 year guarantee period) at the end of April 2011, I returned it to the manufacturer again as it had suddenly developed a loud constant whistle when switched on.Five weeks later, it has still not been returned. I am concerned that I may have a "duff" unit and that more different problems will come to light in the future after the expiry of the warranty period. Do I have any legal rights to ask for a new replacement unit or to ask for an extension of the warranty period?