The maximum sentence for common assault is 6 months imprisonment, of which only half (less any time on remand) would actually be spent 'inside'.
So, at a rather wild guess, a sentence of 3 months imprisonment might be passed, so that's only 6½ weeks 'inside'. Since there would be at least 1½ weeks to come off that (because of the time already spent on remand) it would seem unlikely that the offender would be in prison (if at all, of course) for more than 5 weeks from the date of sentencing.
Chris