Magistrates work from a "bench book" which gives them recommended actions and what are mitigating and aggrevating circumstances which they can use to adjust the sentence.
For Actual Bodily Harm it's 6months and/or a level 5 fine the guideline is of a custody sentence. ( This is for a first time offender pleading not guilty)
Examples of Mitigating factors are cases where there is minor injury, where there was provocation, and where a single blow was struck.
Examples of aggravating factors are cases involving kicking or biting, cases in a domestic environment, headbutting, premeditation where a weapon was used etc.
Given that prisons and custody centres are very overcrowded there's a good chance that they won't want to actually use an actual custody sentence if possible so in an average case I'd suspect a suspended sentence would be most likely.
You want to load the dice as much as possible in your favour - indications of genuine remorse are important, character witnesses etc. You'd probably want to make the court aware of your circumstances and the consequences of your receiving a suspended sentence.
All of these might tip the balance but I suspect the biggest thing will be how bad the actual offense is perceived to be