convert the licence to an EASA one.
Be aware that the conversion from JAA to EASA triggers a whole lot of other things, that may or may not be applicable to you. Yes, it may just be a simple paperwork exercise, but depending on the exact circumstances it may be a whole lot more. One reason is that under EASA all your flying licenses, and all the associated bits (medical, ratings and whatnot) need to be administered by a single *AA, and under EASA a few new ratings were introduced, where you may or may not have grandfather rights.
My JAA->EASA conversion was triggered by passing my IMC rating and wanting this added to my license. In my case it also triggered:
- A change-of-state-of-registry of my medical from the Dutch to the UK authorities (SOLI request) - this also required translations of certain bits of text that the doctor wrote down years ago.
- Addition of a (grandfathered) aerobatics rating (easy thanks to me having participated in a sanctioned BAeA event, fortunately).
- A huge hassle over my LPE. (I had done an actual LPE oral exam and the result of that (LPE-6) was added to my JAR PPL. However, the UK CAA did not want to accept an LPE-6 written on my JAR PPL as sufficient proof of speaking English, to issue me an EASA PPL.)
All-in-all, getting everything sorted took NINE MONTHS. In the end, the mass of paperwork that got sent to the CAA was almost a centimeter thick. (And I'm not done yet. I also hold a Dutch-issued Glider Pilots License and at some point in time that's got to move to the UK CAA as well. That date however is being pushed back over and over again.)