Perhaps the most important thing to remember is that, right now, we can change our minds and pretend that nothing has happened.
Having initiated our desire to quit the Union via Article 50 we had two years to negotiate the way it would work.
It has been adjudged that we can withdraw our notice to leave the Union unilaterally without changing the arrangements we currently enjoy - outside of Schengen, the Eurozone, with our rebate, all of those sorts of special arrangements - the 'Deal' if you will, that we currently enjoy - by revoking our notice to leave the European Union, and to keep that preferential Deal in place.
We have already took the piss twice.
As soon as we agree to any sort of Withdrawal Agreement, as soon as that notice to leave is accepted and enshrined in law, our ability to withdraw our Article 50 application ends.
So if we actually Leave, and realise before the 50 years that Cream-Cracker reckons we'll need to do well out of it, that 50 years is a long time to wait and actually i'm hungry now, we could just as easily reapply to join in Brexit Date +1, or +2 or etc...
Well of course - France and Scotland might have their doubts but we might still have enough friends - we'll have to join the Eurozone though, and completely open the borders to comply with the Schengen Zone, so it won't be quite the same arrangements as before, but we all have to make adjustments to reality don't we?