Jamiroquai seems like an obvious choice given the fact Tramlines and Victorious share at least 2 headliners, but I can't see where he fits in...
Think Paul Heaton pretty nailed on for a spot on the bill, same with Franz Ferdinand. Noel seems unlikely to me, and Jamie T had obviously been suggested to me by a decent source already.
Tom Grennan doesn't really fit the usually sub act, usually more indie band style - think it will be Bloc Party.