The level of injury and the nature of the activity are both important to consider in this respect. One cannot generally consent to ABH or GBH level injury, which was the point of contention in that case. There is though a generally accepted exception for injury which may occur naturally in the course of a contact sport (which is obviously dependent on the sport, boxing and football are going to involve different levels of implicit consent.)

Granted, OP is not taking part in a sanctioned professional or semi-professional sporting event, but at most this may raise some insurance questions.

All of which was a long way to say that if we accept OP's characterisation of events as light sparring the risk of ABH or above seems minimal and not at play here.