To pass the course in minimum time, it'll take you a further 39 hours. (You'll receive a 6 hour concession on training for holding a PPL(A)).
And 2 exams (Principles of Flight and Flight Planning).
But, of course, all of these answers are already in LASORS.
HTH.
PS This applies to JAA. In FAA-land, the (H) is only seen as an add-on to a licence so the training requirements are less stringent (ie shorter!)