Let's say the UK ignores them, crashes out, installs a hard border, doesn't pay the money they owe the EU, what are the real consequences for them? (Other than presumably the RA starting a campaign that afternoon.)
Do they just become some kind of pariah state? The US claims they'd deal with them. Can the EU take action against the UK? I'm guessing they could backdoor something, like insisting on expensive visas for Brits to visit any EU country, various tariffs on goods, generally making their lives as miserable as possible etc.
There's no World Police that goes around making sure debts are paid, agreements are honoured etc. right?