Freeview is the trading name of a company (DTV Services Ltd) which is jointly owned by the BBC, BSkyB and National Grid Wireless. It uses the technical services provided by National Grid Wireless to broadcast programming provided by the BBC and BSkyB. All other broadcasters (whether TV or radio) have to pay to have their signals broadcast by Freeview. (They do this because, if their audience figures increase, they can then charge advertisers more to carry their commercials and thus make bigger profits). GWR, the company who own Classic FM, have obviously decided that they cannot generate enough additional income from Freeview to justify the costs involved.
Chris