You were assaulted and you made a statement to that fact.
The court process is in place and you want to withdraw your statement so that you'll get the cash.
Surely, on the day of the case, you can add to your original statement by saying that you have been offered compensation of 'x' amount, that you are happy to accept it as an admission of guilt/recompense and that you would ask the court to issue a lighter sentence as a consequence.
Going head first into withdrawing your statement in court could risk annoying the Judge who might then decide to make an example of you for wasting court time.
You end up in trouble, statement withdrawn and no money appears.
An offer of compensation ..... ain't hard cash.
Consult a solicitor ... you're looking for detailed legal aid/advice ....... general advice from a forum won't answer it for you.