There's Remand and Bail, basically if you're deemed to be civil you can be released like this guy was, of course if he messes up, he's under remand until the trial.

If you're a flight risk, remand.

If you decide not to return, an arrest warrant will be posted and you will get arrested at some point, even 3 days later when the police knock on your door.

I live near a council estate, see it often for people who've skipped court date being arrested a few days later, one to be fair did miss court due to COVID symptoms and did call ahead, but ... procedure.