Re: "what happens..native UK farming industry if..reduce import tariffs to 0?" " ...
Remember Margaret Thatcher joined the EU
No, John Major did, when he signed up to Maastricht, despite all the opinion polls showing that people didn't want him to.
At some stage with the "EU not working" someone with influence in the EU will decide that current arrangements can no longer stand and propose a new model
And the EU politcians will reply, as they always have, with their mantra of "EU not working, then we need more Europe to fix it". The idea of staying in and making it change worked for a co-operative community, but it has never, and will never, work for a political union that is run for and by the politicians. It would, of course, have been better to change it from within, but 25 years of trying has shown that anyone who tried to rock the boat was simpy ignored. It's what Cameron tried to do, and failed completely. The EU leaders don't accept that it's failing, and so won't listen to any attempt to fix it. It'll take a real disaster to make them see that, and I for one would rather not be in the EU when that happens.
now heading towards a no deal Brexit as an act of throwing their toys out of the pram
EU politicians have long been used to determining everything that happens in the EU, by right. That can be seen in the way they're trying to run both sides of the Brexit negotiations, they simply assume that they can tell the UK how to negotiate, and we'll do what we're told. The only way to make them sit up and pay attention would seem to be the likelihood of a "no deal Brexit". Like any negotiation, if the person you're negotiating with doesn't seriously believe you're ready to walk away they will never make concessions. It's also a curious feature of negotiating with French business people (like Barnier) that only when you lose your temper and shout at them do they actually seem to think "Oh, you're really serious about that". I've seen that in several business meetings. They seem to need a display of passion, and if the UK Brexit negotiators have been doing the classic British icily polite style of diplomacy it could well be misunderstood as a lack of determination or preparation.
I'm beginning to think that the best thing that could happen to make progress would be a handbagging, just have someone on the UK team blow up and state that either the EU gets its act together and starts negotiating on trade or we'll walk away witn no deal, and have the whole delegation just walk out of the room & get on a plane.