There can be no single answer to your question.
Assuming that the matter hasn't already come before a court (and, of course, that the guy isn't banged up in the interim), the police can either choose to release him 'under investigation' or to bail him. If they choose the 'under investigation' route, they can't put any conditions upon where he goes or who he associates with. If they decide to bail him they can impose a 'no contact' condition if they think it's appropriate (but they're not automatically obliged to).
Once the matter comes before a court (and assuming that the guy doesn't plead 'not guilty' and manage to get acquitted), that court will have to decide whether or not to make a 'no contact' order. It's likely that their decision will, in part, be determined by your own 'victim impact' statement to the court but other factors (such as the severity of the assault and the perceived likelihood of it being repeated) will also have to be taken into account.