No, Kingbushido, it is not aggravated burglary 'because of the gbh' ! Burglary is only 'aggravated burglary' if the person commits burglary and at the time has with him any firearm, imitation firearm, weapon of offence or any explosive.No assault is necessary, only the possession of a weapon etc
Ordinary burglary however includes 'having entered a building as a trespasser, inflicting or attempting to inflict on any person any grievous bodily harm' or so entering with intent to inflict it.
Aggravated burglary would be an odd choice of charge in such a case.It's used appropriately for burglars who go out armed to commit theft burglary, not people who visit someone intending to inflict gbh or doing so.It's unnecessary to involve questions of trespass if the charge is simply 'attempting gbh'(there is no gbh described here) or, better, 'wounding with intent to cause gbh' or just 'unlawful wounding' and the prosecution should proceed on one of those.
The tape is relevant to show intent on the part of Gill to inflict harm. Of course, it may not explain why someone who was aware of that would go to visit the malicious individual ! His visit suggests that the accused was braver than most or reckless or that he did not take the threats literally. In any case, on his version he has not been a party to any assault but was an innocent bystander with no intent that anyone be assaulted and should therefore contest any charge.