I was just wondering whether I will be expected to pay them to change my JAR FCL PPL to EASA soon?
As far as I understand, no.
Your JAR-FCL PPL will remain as-is, with no need to exchange it, until the normal five-year period is up. You then renew it as usual, only what you'll get in the mail is an EASA PPL. And you'll need to pay the usual charge for this.
You are still bound by EASA rules though, even though it still says JAR-FCL on the booklet.
So it all depends on when your PPL is due for renewal whether it makes sense to wait. And, of course, you can always renew your PPL ahead of time.
(The good news is that EASA PPLs are lifetime PPLs, so no need to renew them every five years.)