I believe I need an Auth or EPP code
You only need an EPP code if it's a non-uk domain. Otherwise you just need the IPSTAG changed to the new registrar.
Either way , here is the place to request it. A staff member will be along in due course and will either raise a ticket or a PM go request the relevant information
Superusers are not staff, but they do have a direct line of communication into the business in order to raise issues, concerns and feedback from the community.
