With Merkel whinging from TDS in the corner and Macron popularity plummeting through the teans there is a chance Parliament can be encouraged to do the right thing.
https://www.express.co.uk/news/politics/1104092/brexit-news-emmanuel-macron-mocks-leaving-would-be-easy
As I understand it without approval of this extension Article 50 stands and the 3-29 WTO exit will happen. Then the UK-EU relationship will continue on GATT Article 24 terms with no tariffs while they realign their treaties.
I like this option best but I'm not in the UK and I don't expect Macron to act like a grown up by himself.