I don't want to play devil's advocate here, but it's unlikely that anything will be done. Logistics and primarily cost mean a resit isn't feasible (exam boards are designed to make money plus Edexcel is privately owned).
Any discrepancies in grades can easily be down to actual revision not cheating so that method is out. They could call for students to be awarded their mock grade but that means that you render any revision done between then and now useless. This also calls the authenticity of internal mocks into scrutiny.
Just my thoughts. I think that, realistically, nothing meaningful will be done as the full scale of malpractice will be almost impossible to uncover.