Maybe should have it's own thread.
My answer would be: there'll be furious dealing to put together an alternative deal, which will either be ...indistinguishable from the current one, or the Norway model ( no plus, no say, contribute danegeld as per-usual), or Canada ( which has been in place for about a year and took ten years to negotiate is scarcely different to no deal).
And of course the food-aid shipments to the UK.
We'll see how it goes on Tuesday. Failing that....second referendum seems the only way to avoid no deal.
If no deal happens, I think there'll be a bunch of small emergency deals to keep planes flying, etc. but it'll still be a disaster. Food and Energy security in the UK will be severely pushed, riots won't be far behind.