Hp.
Not sure who you work for, but if I read it right you currently operate Greg ac on a UK licence? So that’s ok so far and it would only become an issue if you went to a non uk airline.
If that’s not part of your current master plan then perhaps sit tight for a while and see what happens - it’s not impossible that there will be mutual recognition of licences in the future.
Bit of detail on TRE stuff. As EASA TRE I can sign EASA and UK licences. UK at least until end 2022 or expiry of my current certificate. Now that the CAA is going to allow UK licence issue to previous holders from (I think) Apr this year my company will doubtless ask me to do this for full flexibility. So, having surrendered my uk licence at the end of last year for IAA I will probably soon be going back for a reissue. Hopefully with my old CAA number.
Good luck