Steve Denyer was talking about Glastonbury headliners on his radio show yesterday. He said that Madonna, Stevie N and Stevie W have all been engaged in headliner discussions at some point for this year and all fell through.
I don't know if he has any insider knowledge but he did say it with some authority/ as a matter of fact rather than hearsay. He's been in radio for years so wouldn't be beyond the realms of possibility he did have some insight but could equally be no better sighted than the rest of us.