We don't need any more concrete proposals
"Free speech campaigners said that amendments to the draft Defamation Bill should include "concrete proposals to stop legal threats against internet hosts bringing down entire websites," a spokesman for the Libel Reform Campaign said, according to the BBC."
Perhaps I'm missing something. (My first language is English rather than legalese, so it is perfectly possible.) But presumably it is already the case that no web-site is stupid enough to edit someone else's remarks and then present them as though they were original. That requires much more effort and judgement than the safe alternatives of either publishing as-is or refusing to publish at all.
If we now add a "conduit" defence in the new law then it will be common knowledge in legal circles that all such cases are groundless and therefore anyone bringing one is knowingly wasting the court's time and deserves to bear all costs and be marked down as a vexatious litigant for good measure.
Even if that isn't enough to stop some idiots, they'll only be able to do it once.
(Icon: I Am Not A Lawyer, but this is the closest icon I could find.)