Here's the document which judges are obliged to refer to:
http://www.sentencing...person_accessible.pdf
See page 17 for the guidelines on sentencing for ABH. (It should be noted that those sentences refer to a first-time offender, convicted after a trial. Higher sentences can be passed on an offender with previous convictions).
It's likely that any sentence for the criminal damage offence would be concurrent, so you can just refer to the guidelines for sentencing ABH.
I'm amazed that the charge isn't 'GBH'. See paragraph 45 onwards, here, to compare the difference:
http://www.cps.gov.uk...he_person/#P189_14382
My guess (based upon the information you've provided) would be a sentence of around 12 months (of which 6 months would actually be spent 'inside').
Chris