There is a policy now of prosecuting domestic violence even if none of the people involved are prepared to make a statement. The prosecution can proceed just on the evidence that was found, In this case the photos and the blood on the floor . Photos /descriptions of your and your wifes injuries can be used as evidence and the statement from the neighbour.
ABH S 47 is not a serious offence I think it is magistrates court only , it is almost impossible for it to be a prison sentence . Remember you get an automatic reduction of 1/3rd in the sentence for an early guilty plea. As you did actually cause harm, I think that IF and only IF this goes to court a guilty plea is your only viable option. You will almost certainly get a small fine or very low community service order possibly suspended may be even just a conditional discharge.