I think there is still confusion about whether a CPL is needed or not for a FI course!
What the regulations say is that you need to meet the knowledge requirements of a CPL (ATPL ground studies will do it) but a PPL and an appriate flight time loged is fine! No payment though. To be paid, you need a CPL.
http://www.jaa.nl/jar/jar/jar/jar.fcl.1.335.htm
I might be wrong! If so I apologise!
TheNavigator