I'll admit up front I'm no singer and even worse at doing accents. To me, as I've grown up, I've come to dislike singers singing in affected accents more and more. Much of English pop seems to be sung in a psuedo US accent and it's always a pleasure to hear pop sung in an English voice.

Folk is the same, I'd rather someone sing in their own accent (unless they've totally mastered mimicing the "foriegn" accent) and where necessary translate a dialect phrase or word. For example I love Bonny at Morn but when I sing it (for my own pleasure well away from anyone else) using a word like kye is, and sounds, ridiculous in my Middle Saxon accent.