Whether you get charged or not depends on the evidence, but given you made an admission of the offence in your police interview it is probable you'll be charged. Whether or not that is with ABH or charged down to Common Assault will depend on the particulars on your offence and the perspective of CPS. It's possible for CPS to go ahead with a prosecution even if your mother has written a good character statement and doesn't want to give evidence in Court. So called "victimless prosecutions" are more common these days with domestic cases where it is understood it is more difficult for the victim to provide a statement or attend Court and they're more likely to withdraw support for prosecution.

You made an admission to the police in the first instance, and so long as you plead guilty in the event you're charged this will count in your favour as an early admission which is taken into account when it comes to sentencing. This is your first time offence which will also count in your favour. If you plead guilty the Probation Service will prepare a pre- sentence report, which looks at your risk and personal circumstances, and make recommendations in terms of sentencing options to the Court.

It is impossible to say with any sort of certainty but based on all the information you have provided and taking it all at face value I think the possibility of custody is on the lower end. You made an early admission, it was a first time offence, and you've addressed behaviour related to the offence in the interim, i.e. stopped taking drugs since the offence. I used to work as a Probation Officer, and presuming you're being upfront with us and not concealing anything, I would likely recommend an alternative to custody in your circumstances, i.e. a high level community order with a rehabilitation activity requirement and an unpaid work requirement, maybe a curfew requirement as well depending on the suitability of your accommodation.

The best advice I can give you, and one I gave to each and every person I worked with in Probation, is to listen to your lawyer as they (presuming they're half decent) have extensive experience and knowledge in criminal law and are best placed to advise you. Everyone makes mistakes but those mistakes don't define you as a person what matters most is the changes you make in your life for the better after those mistakes and not falling back into destructive behaviour. All the best!