I've thought for sometime now that we're watching a pantomime with May's 'negotiations' and there were two possible outcomes.
A) Parliament votes for the 'deal' and we get BRINO on 29th March. In the following trade talks during the 'Implementation Period' the EU make impossible demands and as the UK has agreed that the EU control the sequencing of the talks, the EU refuse to 'move on' until specific issues are agreed. Fishing rights for example. On 31st December 2020 there is no agreement on a FTA and the UK goes into the 'Backstop'. TTIP talks are revived with the US and the EU agree that US chlorinated chicken can be sold in the UK. The British press scream blue bloody murder, but the UK government are powerless to intervene. A referendum on rejoining the EU is held and the question is Status Quo or Rejoin. The UK votes to rejoin and the EU agrees to fast track the process...... with conditions.... no rebate, join the Euro and Shenghen.
B) Parliament rejects May's deal. Chaos ensues and to avoid the perceived disaster of leaving with no deal, Parliament votes to extend the A50 period. The EU readily agrees, but refuses a short extension and demands that the UK stay until the end of the current financial framework which secures their money and on condition that Britain holds a second referendum. The UK agrees but during the extension the EU is as inflexible and intransigent as ever and we approach December 2020 with no agreement in sight. The weary Brits vote remain in the second referendum and despite the ECJ's ruling that the UK can revoke A50 and remain in the EU without penalty, Britain comes under intense political pressure to relinquish the rebate in the Multi Annual Financial Framework talks. Prime Minister Corbyn agrees to give up the rebate, Chancellor of the Exchequer McDonnell starts talks to take Britain into the Eurozone and on the day the Queen dies, Home Secretary Abbott quietly announces that Britain has signed up to the Shenghen agreement.
Voila!