An IR is an IR no matter what licence you hold, Private or Commercial. The IR exams are the same for PPL Holders and CPL holders.
Yes the old National PPL/IR is dead, but the JAA IR is here to stay and you can add it to a PPL or a CPL.
Details in LASORS 2003 Section E:
http://www.caa.co.uk/docs/175/Lasors_Section_E.pdf