Page 201 of this document give the sentencing guidelines:
http://www.sentencingcouncil.org.uk/wp-content/uploads/MCSG_web_-_October_2014.pdf
It’s difficult to say from your brief description which category the court would view this offence. It could well fall into category one (the most serious). If so your ex is looking at a custodial sentence without doubt. Even if it is classified Cat 2 custody is a serious possibility.
However, there are two other very important things you need to ensure:
Firstly make sure you provide a “Victim Personal Statement”. This gives you the formal opportunity to say how a crime has affected you. The court is obliged to consider its contents and take it into account prior to passing sentence.
But most important of all you need to ensure he is kept away from you in future. Make it clear you want a “restraining order” imposed and that you want it made “until further order”. This means it will last indefinitely unless you both agree to it being lifted.
Witness Care should help you with this and the “officer in the case” (police) should make sure you are in touch with them.