>>> Easy Answer to the BBC, Advertise, simple.
Where is all of the advertising revenue going to come from?
With the advent of the internet (and social media in particular) the total amount of advertising revenue available to TV broadcasters has dropped dramatically at a time when the number of broadcasters trying to get a share of it has increased considerably. So, for example, the 'real terms' revenue available to ITV has fallen by over 90% (which is a really MASSIVE cut!). ITV struggles to survive and has made it quite clear that it would go out of business if it had to share available advertising revenue with the BBC channels. Similarly, lots of other stations would also have to close down. (The vast majority of British TV stations operate 'very close to the edge' financially).
Anyway, the BBC already raises money through advertising via its commercially-operated channels. UKTV (Alibi, Dave, Drama, Eden, Gold, Good Food, Home, Really, Watch & Yesterday) is the BBC's commercial arm, co-owned with Scripps Networks Interactive.