Taking over from letting Agent

Letting Agents

HI All,
New member and first post.
I have written to my LA today advising that I intend to take over the management of 2 of my properties from March 23. No issues with the service they have provided but going forward would like to self-manage. This will be my first venture into self-management, so I am learning as I go - got to start somewhere. They have written back advising of their fee to "hand the tenancy back to me " which I was expecting so no real concern there. I am aware of my new obligations as a landlord and intend to get all this in place in good time prior to notifying the tenants of the change in January . The LA has asked for my GDPR certificate before they will release anything over to me. Apologies for newbie query but am I correct in thinking I need to apply for this from ICO over and above completing a Privacy notice ? Also what's involved in becoming certified? Yes, I also appreciate perhaps I should have fully understood this before writing to my LA . Hopefully you guys can offer some constructive friendly advice . Thanks