You've not stated why the case is before the Crown court. ABH is an 'either way' offence, so it might be that your former boyfriend has elected trial by jury as he (or his solicitor) believes that he might have a better chance of being acquittted. Alternatively, the case might have been referred to the Crown court because the magistrates believe that it's outside of their jurisdiction. They'd normally only do so if they thought that, if the defendant was convicted, their sentencing powers would be inadequate. So, if the latter circumstances apply, the court has already indicated that, upon conviction, a prison sentence exceeding 6 months would be likely.
Without knowing the exact circumstances it's hard to give an accurate estimate of the likely sentence but he's probably looking at a sentence somewhere between 12 and 30 months, with around half of that time actually being served. So, with a bit of luck, you won't have to see him around for quite some time.
Chris