You've provided insufficient information. The decision whether to charge under 'Section 39', 'Section 47' or 'Section 20' is determined by the nature of the injuries sustained, not by the manner in which they were sustained. (You can punch someone once, causing bruising and be charged with 'common assault'. But if your action results in a displaced fracture of their nose you'll be charged with 'ABH'. If you cause a compound fracture of their jaw you'll be charged with 'GBH'). You've made no reference to the level of injuries, so we can't answer your question.
See paragraphs 13 (Common Assault), 46 (ABH) and 55 (GBH) here:
http://www.cps.gov.uk..._the_person/#P92_3540
Chris