A few things need pointing out, JayRed.
Firstly, ABH is an “Either Way” offence and you have not said whether your case is to be heard in the magistrates’ court or the Crown Court. You do not have to prove your innocence, the prosecution has to prove your guilt beyond reasonable doubt. ABH most certainly does require proof of injury to secure a conviction. Whilst photographic evidence is not necessary, statements alone will not suffice. If you disagree with anything in any statements the witness must attend court, give evidence and be subject to cross-examination.
Contrary to TheHouseHusband’s doom laden prophesy, your previous conviction should not influence your sentence if you are convicted. It is too old and the judge or magistrate is not entitled to take it into account, whatever side of the bed he may have got out of or what his social upbringing.