My licence is a blue UK CAA Flight Crew Licence. Within in it, my licence number starts GBR.FCL.AT.xxxx.
No problem. All UK-issued Part-FCL licences such as yours are now deemed to be UK Part-FCL licences and no conversion is needed if you wish to fly G-registered aircraft.
Unfortunately, I temporarily lost my medical nearly 2 years ago. I am now heading in the right direction to getting it reinstated.
Excellent news! All you will need to do in order to exercise your full ATPL privileges is to renew your Part-MED Class 1 and to renew your Type Rating and IR.
NO exams are required.