Hi,
As far as I know, you can still transfer, why not? You can do this until Friday 29/3. The problem is that the CAA is overwhelmed with the requests, and it takes longer than usual for them. Hence they will transfer to the IAA. However, not in time as to continue flying in April, but likely a few weeks later. All this in case of no-deal or no interim EASA agreement, talk about a few months of grace period is on the way.
Let as know about what you are told on Monday...
Cheers