FD - the use of ILS is not covered during the PPL syllabus of trianing, whereas the use of en-route navigation aids is. A procedural approach, using ILS, requires the pilot to fly using the instruments. That is why a safety observer must be carried in order to avoid conflict with other traffic under VFR.
The use of PAPIs and the use of ILS are fundamentally different. One requires 'head out' and assists a visual approach, the other requires 'head in' to follow the ILS display.
A VFR-only PPL holder 'practising' an ILS approach in VMC without proper training and without a safety observer would be a very foolhardy person indeed.