In April 2021, the Ministry of Justice released a "Victim's Code".
Among other things, it says:
You have the Right to be provided with updates on your case and to be told when important decisions are taken. You also have the Right, at certain stages of the justice process, to ask for decisions to be looked at again by the relevant service provider.
This is elaborated on, including:
If the police decide not to investigate your case, you will be given an explanation of this decision within 5 working days (1 working day under Enhanced Rights). The police will also offer you a referral to a support service.
Where the police or the Crown Prosecution Service are considering an out of court disposal you have the Right to be asked for your views and to have these views taken into account when a decision is made. Where this is not possible for practical reasons, the police or the Crown Prosecution Service will tell you why
If you are unhappy with a police or a Crown Prosecution Service decision not to prosecute the suspect, you have the Right to ask for a review under the National Police Chiefs’ Council or Crown Prosecution Service Victims’ Right to Review schemes.