I presume the thinking is that you are flying with student pilot status.
That is not the CAA's view - you cease to be a student pilot as soon as you are in receipt of your licence. The current guidance on solo flights after completing the skill test is
here and, in particular, para 6. states:
Once the student pilot is in receipt of their licence, unless the licence is a Light Aircraft Pilot Licence (LAPL) or otherwise instructed by the UK CAA, they are not permitted to be authorised solo by the Flight Instructor for future flights.
Which seems to say that you cannot be authorised to fly solo in preparation for the class rating proficiency check.