I'm not so sure it in the UK's hands, any more.

The EU gave them until October to come up with a viable plan for exit. Article 50 was triggered, and has been extended twice. I'm slightly hazy on what happens if the country triggering Article 50 just fails to do fuckall, like the UK has... but I think the EU ends their membership: aka, Hard Brexit.

In a future where Britain cancels Article 50, I expect the EU comes down like a ton of bricks on them, and forces the UK into the EMU, and rescinds many of the special allowances they have had to make in the past. The UK has clearly been negotiating in bad faith, so all of the workarounds the EU has made for 50 years to appease the damp northern whiners will no longer be easy to maintain.

A chastened UK is not a participatory member of the EU, and will not be operating in good faith with the rest of the member states.

You don't get to storm out of the house in a hissy fit, go fuck other women, and then come back home and act all penitent and expect your wife to take you back in.

Fuck that guy.

(This is me, putting on my "EU Minister" hat, and speaking for the EU.)