That's correct.
As of the 01 Jan this year EASA Licensed Engineers can no longer certify work on UK (G) registered aircraft and UK CAA Licensed Engineers can no longer certify work on EASA registered aircraft.
This becomes a bit problematic if you've got a small line station with only one or two engineers.
There's still more fun to come in the future, you can still fit parts certified with an EASA Form 1 till the end of 2023, after that you will require a UK CAA Form 1. I can see component manufacturer / overhaul companies having to issue triplicate releases in the future (EASA / FAA / UK CAA).
So in brief, more exams, more paperwork and more expenses !