Most Times and Sunday Times readers have no idea that they are buying Labour-supporting papers, and would switch to the Telegraph if they ever cottoned on. However good Sky News might be, hardly anybody watches it. Apologies to Fraser Nelson, but no one ever bought the News of the World for the politics.
And as for the Sun, half of its readers always did vote Labour, while most of the other half had already decided to do so a period of years before it followed suit (or, indeed, before anyone other than political anoraks had ever heard of Tony Blair) in order to preserve its privileged access to Ministers. If it is now pro-Cameron, then that is for the same reason.
The real story is that Andy Coulson sashayed effortlessly from editing at least notionally a Labour-supporting paper to being Cameron's Head of Communications. Such is the One-Party State of Britain, now so entrenched that no one even remarks on it any more.