There is nothing so far confirmed a Transition period has been talked about but until its legally binding and approved by both sides I wouldn't bet on it.
Also don't touch the Spanish CAA with a poo pole, everything takes months to sort out and many many brick walls to bang your head against also its one of the expensive authorities. I have had several mates transfer away from them.
CATS don't have a clue either what's going to happen same as the rest of us. They have to say that other wise nobody in their right mind would start training with them or any other UK approved provider for the next year if the person intends to use their license in euroland.