Unfortunately it is not as simple as saying you don’t want to proceed anymore. The English process does not work like that.
When you report abuse, the police will arrest the perpetrator and investigate, and if they have enough information, they will pass that information to the Crime Prosecution Service (CPS) who are the ones who make the decision as to whether or not to prosecute the perpetrator.
Usually they will already have the victim’s statement, any body cam evidence that was collected at the time of the report/arrest, eye witness accounts and statements, and potentially medical evidence, or photographs of injuries. So even if you decide you no longer wish to proceed, they can do so without your cooperation.
You can of course notify the investigating officer that you wish to withdraw your statement, and say that will not support a prosecution, but that doesn’t stop them from proceeding if they believe they have enough evidence. If you are the only witness, then the chances of the case being dropped are higher than if there are several witnesses, especially if independent, and other corroborating evidence.
I am sorry this will obviously not be the news you were hoping for, but it is how English law works in this instance.