If it fails .. not necessarily fine at all. We'd be back to seeing the Commons in session.
There was one point during the last session when the Commons voted to order the Prime Minister to go to Brussels to ask for an extension to the Brexit deadline. Duly 'commanded' by that vote, (though in that instance she wanted that extension, herself) ... she 'obeyed' the Parliamentary mandate and made that request of them.
Boris might find himself facing another such vote, whether he wants to or not, and losing it. He'd then be mandated by Parliamentary vote to go to Brussels and totally defy the promise of '31st October, come-what-may' he's already given.
Here's a report of when Mrs May received her Commons 'command':
https://www.9news.com.au/world/brexi...c-d72e3993af78
Such a request could be tabled for a vote by any MP, however.British MPs have voted to delay Brexit beyond the scheduled date of March 29 amid dramatic scenes in the House of Commons.
The vote came after Prime Minister Theresa May's Withdrawal Agreement was rejected for the second time on Tuesday and MPs voted the following day to rule out a no-deal Brexit.
A motion in May's name, authorising her request for an extension to the two-year Article 50 negotiation process, was passed by 412 votes to 202 - a majority of 210.
Only a refusal by the leaders of the 27 remaining EU states to grant the UK an extension at a Brussels summit next week could now preserve the totemic date of March 29 as Brexit Day.
May has made clear that she will press her Agreement to a third "meaningful vote" in the Commons by March 20 in the hope of securing the support of MPs who rejected it by 230 votes in January and 149 earlier this week.
If she succeeds, she will go to Brussels next Thursday to request a short delay to a date no later than June 30, to give herself time to get her deal through the UK parliament.
As for your other scenario, one of the No Confidence motion succeeding, an election is called, then the Brexit date passes before the election date ... yes, you'd think that would be the answer. Corbyn has anticipated that outcome, though, and has been trying to fight it, as follows:
https://www.msn.com/en-gb/news/brexi...xv7t?li=AA59G2
I don't know if there's been a decision, one way or the other. It may be that the Summer Recess is delaying publication of the decision reached.Jeremy Corbyn has called on the UK’s most senior civil servant to intervene to stop Boris Johnson forcing a no-deal Brexit in the middle of an election campaign, amid rising signs the country is heading for the polls again this autumn.
The Labour leader wrote to Sir Mark Sedwill, the cabinet secretary, accusing the prime minister of plotting an “unprecedented, unconstitutional and anti-democratic abuse of power”, after it emerged No 10 would be prepared to delay an election until immediately after 31 October if Johnson loses a no confidence vote among MPs.
In his letter, Corbyn demanded urgent clarification of the rules around purdah, which are meant to prevent the government taking major policy decisions during an election campaign.