You can be summonsed as Ethel has said. Of course when you do give your evidence you can also �forget� the details of the events. A reluctant witness if often less use than no witness at all.
It is not good enough for him to be complying with his current bail conditions for one important reason. Once the case is over (whatever the outcome) his bail conditions will be removed. This means that unless he is convicted and a restraining order is imposed as part of any sentence he may receive, he will be free to resume contact with you and (probably) resume his activities against you.
If there are no other witnesses to the assault upon you the prosecution may well decide not to proceed against him. Even if they do proceed, the likelihood of a conviction is considerably reduced without your testimony. So, no conviction, no restraining order and back to square one for you.
If you really want this sorted out, go to court and give your evidence. As Ethel says, Victim Support will help you. They have a Witness Support service to help you specifically when attending court and they will look after you on the day.