speak to legal aid/lawyer and see where u stand into making boho bar pay for damages, they have a duty of care and releasing violent drunk people out onto the street may break this??? long shot but hey, cant hurt to atleast speak to people.....
remeber there faces, go back there in a few weeks, wrech in the pants, wait till one of 2 of em leave and give em a few "smashed windows and kicked panels"
but seriously i would be hounding the venue and use the police as ur friends here (if the pricks actually do something about it)