Carole, if you still have the bruises, you might want to consider taking some pictures or asking a friend to take them. So if you to decide to take it up with the police, you'll have some extra ammunition. Do you know any of the other women who were assaulted? If so, you should be asking them to write down what they remember about these men and what happened.Even if you're undecided now about whether you'll make a complaint (against the assaulters or against the venue), if you think it's possible that you will, it's best to collect evidence (the pictures, or written accounts of the incident) sooner rather than later.
Marion