It is proposed under part-FCL 2008-17b at FCL.205.A PPL(A) Privileges that the holder of a PPL(A) may receive remuneration for the provision of flight instruction.
Subject to meeting the FI course entry requirements (which do NOT include the requirement for CPL knowledge) and passing the FI Skill Test, it is proposed that it will be possible to add a FI 'Certificate' to a PPL(A).
But not for about another 4 years......