Hard Brexiting: Telling everyone you're leaving the party as two bouncers are tossing you out
Soft Brexiting: Telling people you want to leave the party but insisting you are taking all the booze and music with you and demanding the other guests pay for your taxi home.
Edit
May Brexiting: Saying you have left the party while still supplying the music and booze but only being allowed to sit in the kitchen and not talk to anyone.
Farage Brexiting: Moving half of the party to a closed down pub in the next town because the first party had the "wrong" DJ and didn't have real ale.