The CAA have published the following:

“Last date for ATCO applications based on EU, EEA and Swiss licences issued under commission regulation (EU) 2015/340 credits

Individuals wanting to gain a UK Air Traffic Controllers (ATCO) licence, based on credits from having met the requirement for the issue of a licence in accordance with Commission Regulation (EU) 2015/340, should be aware that final acceptance date for an application based on these credits is the end of the EU transition period, 31 December 2022.

We are not able to extend the date without conflicting with the Savings Provisions of the EU Withdrawal Act.