How to assign new AEDM

I'm retiring soon and am trying to assign the role of AEDM to the person who is taking over the MOT Station.
He has done all his courses, returned all the forms with the necessary paperwork & checks and apparently it's all on the system waiting for me - the current AEDM - to assign the role of AEDM to him which he then accepts.
When I go onto the system and try to assign the role to him it only gives me the option of assigning Authorised examiner delegate or Authorised Examiner Consultant   --   there is no option for AEDM?
I phoned them for help and she said everything was on his record but she couldn't help as I need to speak to MOT administration for which there is no phone number apparently I have to email them if I have a query --  any ideas what that email might be or has anyone else assign an ADEM role & can tell me how to assign the role?