//Thanks for answers All makes since //
It doesn't really because you haven't been given answers to the questions you raised (and some that you didn't).
You do not have to provide a statement. You can do so voluntarily if you wish. If you do, there's a few things you should be aware of:
1. If you are interviewed under caution by the police (and they must caution you if they want to use anything you say as evidence) you are entitled to have a solicitor present. You do not have to pay for this.
2. "Assault" does not have to necessarily involve physical contact. An assault is "...any act by which a person intentionally or recklessly causes another to suffer or apprehend immediate unlawful violence." The critical phrase is "...causes another to apprehend immediate unlawful violence." If someone believes they will suffer violence, that is enough to make out an assault charge.
3. If you are to be charged with Common Assault (and from your description there seems no injuries evident which may support a more serious charge) the police must begin court proceedings within six months of the date of the alleged offence. That's why I asked what the exact date of the incident was. If it's taken them five months to get round to contacting you and they need another week before they interview you, they don't have too much time left before you can tell them to go forth and multiply.