First off, I'm sure we've had threads like this before which I can't find, so feel free to just link me to them. Failing that:
My mate works as a teacher in Taiwan, and has some older students who want to listen to popular English music (I don't know whether specifically English or English-language). He wants to come up with some bands (I'm going to take a vaguely rockist/indie approach) that sing without heavy regional accents (blah blah everyone has an accent whatever) that would be suitable for English learners.
What have ya got?