The fact that he was drunk will aggravate the matter in the eyes of the judge or magistrates. He may be able to offer your provocation as mitigation.
Although this offence is not, strictly speaking, one of domestic violence, it may well be viewed by the Crown Prosecution Service (CPS) in the same light. They have policies which enable them, in certain circumstances, to continue such a prosecution even if the alleged victim withdraws his or her statement. Your withdrawal will not automatically mean that the prosecution is discontinued. This is set out in their document:
http://www.cps.gov.uk/publications/docs/Domest icViolencePolicy.pdf
Paragraphs 5.9 to 5.27 are particularly relevant.
You should also note from that document that if you do retract your statement enquiries will be made into the reasons why you have done so.
Only the sentencing judge or magistrates can say whether prison is a certainty. However, in terms of Criminal Damage, the value of �8,000 makes this a serious offence and sentencing guidelines certainly suggest that custody must be considered.