Oh jeezuz Mark, i'm fuming to hear this.
When did this happen mate? today?
Sad symptom of our society that a-holes like them only prey on the weakest looking and least likely to give them a good hiding.
Oh how i wished i'd been there mate
Abd sadly you're right about the cops but do consider it this way, if you do call them they may be spotted on CCTV locally and already be known to cops who will be able to deal with it. You know that incident i had recently, well thats how they caught up with that group of kids, local CCTV. Its worth considering just letting them know mate.