Now that mamjet is feeling a self-righteous glow at your expense I'll try and answer the question for you!
The magistrates guidelines for ABH for a first time offender pleading guilty is a custodial sentence. But the quoted mitigating factors are :minor injury, provocation, single blow etc. all of which seem to apply to this case.
If these are stressed and the court see the events in a similar way to how you describe them I'd be surprised if he received a custodial sentence.
I am a bit surprised that he was charged with ABH if the other guy only had bruising - I guess it must have been bad