"With just a PPL you can't be paid to fly"
But come this april you will be able to.
You're talking about a small exception case (PPL holders with an Instructor Rating), but I can't imagine there will be many of them because you will still need to meet the CPL theoretical requirements and have received 10 hours instrument instruction in order to commence an FI-R course. So more often than not these people will be CPL holders.
I'd imagine that, other than a handful of exceptions, the only PPLs that are going to receive payment post April are those BCPL (with an FI rating) holders who's licences automatically become a PPL under EASA.