Singing in Plain English

I've always wondered why English people never have an accent when they sing. Sure, there are those few that have a really strong accent that comes through when they sing, but for the most part, unless you hear singers speak, you might not know they were from England. For example, Jay Sean, a British singer, has a really popular song out right now called "Down," but I had no idea he was from England until the radio announcer said he was. I'd never actually heard him speak until a few days ago when they played a clip of him talking on the radio. Then they played his song, and it was so strange to listen to his heavy British accent and then to hear his song. It seems to be a pretty general trend, though. The Beatles, one of my favorite bands, is from England, but their songs don't suggest their British roots. I wonder if British people think the same thing about American singers.