And that's the fundamental disconnect. The BBC is not getting a free ride. They are paying for the bandwidth they use - through their own ISP & CDN bills.
Granted, it's probably not the same provider, however why should that matter? They're paying to get that bandwidth somehow. They shouldn't have to pay even more to every little provider so their traffic is not deprioritized.
If the ISP needs more money, they should charge their users more. They're the ones using the bandwidth - not the BBC.