So what happened in this case was that STJ 1 & then 2 both indicated that they wouldnt accept a withdrawal on the basis that only the DOH could make it.
I pointed out the definition of party in a long letter and the very helpful STJ Rickman dealt with the matter and consented to the withdrawal. I also spoke by phone with STJ Chahal afterwards who confirmed that this approach was correct and a DOH referral can be withdrawn by the patient because they are a party to the proceedings.