Basically, you can come down to three things in this 'mess':
1. PM May probably will have to call for a new election to occur, and likely will be toward November. She might be able to stall this for six weeks, but the longer you get along and closer to BREXIT....the hostility among the Conservative leadership will just get worse. So, she's gone by the end of 2018.
2. BREXIT occurring with a treaty, by the deadline of 29 March 2019? Once you get to the election idea....then they can't meet the deadline, and there is virtually no chance of a signed treaty.
3. The involvement of the Tommy Robinson episode in an election? Well, that's the odd factor. UKIP might now find a real topic besides BREXIT, and you might suddenly find a quarter of dependable voters for the Tories and Labour.....suddenly siding with UKIP.
So I come to this question....what really happens after 29 March 2019, if there is no agreement? Who gets hurt the most? England? Or France/Germany? Does Trump hold some card in this peculiar poker 'game'?