Torrent streaming is very efficient for the server costs, However you have to stop trying to lock everything down somewhere because though it's a nice thought it only annoys the legit users.
In the end there is no way to stop someone just "dubbing" the video manually if there are a million software blocks in place, If you can see it you can steal it, Is the way media goes.
All the anti-piracy protections hurt more consumers who pay than the pirates who won't be worried by it once they have it.
However more to the point, Torrenting would be a wonderful alternative especially if it was made aware to the users that by leaving it streaming they'd HELP the BBC, It'd make for great content distribution.