//yes but what would be the legislation?//
Exactly the same as last time with the Cooper/Letwin shenanigans, 3Ts. As I repeatedly have said, there is no way that the Commons will allow a "No Deal" exit to go through by default. Messrs Hunt and Johnson are suffering delusions (or, at least, trying to delude the electorate) if they believe that No Deal will occur either on Halloween or at any time in the future.
Nobody wishes it more than me. The recent "appointments" to the top table in the EU have demonstrated exactly which way it is heading (take note those who believe to Remain is to continue with the status quo). The agreement between the EU Parliament and the Commission has been unceremoniously ditched because the Parliament is no longer "on side". But more than that, the EU's treatment of Switzerland over the last few weeks portrays exactly what non-member nations with bilateral agreements with the EU face. They face the jurisdiction of the ECJ, they face bilateral agreements being torn up and they face forced "equivalence" with the EU and all its mantras or be cast adrift. Any agreement that we forge will not be worth the paper it is written on because, the parts to our advantage will be, bit by bit, dismantled.
The EU doesn't do consensus. It rules from the centre and from the top down. We need to leave, we need to leave now and we need to leave properly. Only then will we be able to make our way in the world as an independent trading nation free to trade with whom we wish on the terms that suit us. The Commons will not allow it and they will never be forgiven. But they don't care a toss.